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Patch "bpf: skip unnecessary capability check" has been added to the 4.9-stable tree

by gregkh＠linuxfoundation.org

This is a note to let you know that I've just added the patch titled bpf: skip unnecessary capability check to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=sum… The filename of the patch is: bpf-skip-unnecessary-capability-check.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable(a)vger.kernel.org> know about it. >From 0fa4fe85f4724fff89b09741c437cbee9cf8b008 Mon Sep 17 00:00:00 2001 From: Chenbo Feng <fengc(a)google.com> Date: Mon, 19 Mar 2018 17:57:27 -0700 Subject: bpf: skip unnecessary capability check From: Chenbo Feng <fengc(a)google.com> commit 0fa4fe85f4724fff89b09741c437cbee9cf8b008 upstream. The current check statement in BPF syscall will do a capability check for CAP_SYS_ADMIN before checking sysctl_unprivileged_bpf_disabled. This code path will trigger unnecessary security hooks on capability checking and cause false alarms on unprivileged process trying to get CAP_SYS_ADMIN access. This can be resolved by simply switch the order of the statement and CAP_SYS_ADMIN is not required anyway if unprivileged bpf syscall is allowed. Signed-off-by: Chenbo Feng <fengc(a)google.com> Acked-by: Lorenzo Colitti <lorenzo(a)google.com> Signed-off-by: Daniel Borkmann <daniel(a)iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- kernel/bpf/syscall.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -801,7 +801,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf union bpf_attr attr = {}; int err; - if (!capable(CAP_SYS_ADMIN) && sysctl_unprivileged_bpf_disabled) + if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN)) return -EPERM; if (!access_ok(VERIFY_READ, uattr, 1)) Patches currently in stable-queue which might be from fengc(a)google.com are queue-4.9/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch queue-4.9/bpf-skip-unnecessary-capability-check.patch

7 years, 8 months

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Patch "kbuild: disable clang's default use of -fmerge-all-constants" has been added to the 4.4-stable tree

by gregkh＠linuxfoundation.org

This is a note to let you know that I've just added the patch titled kbuild: disable clang's default use of -fmerge-all-constants to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=sum… The filename of the patch is: kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable(a)vger.kernel.org> know about it. >From 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann <daniel(a)iogearbox.net> Date: Wed, 21 Mar 2018 01:18:24 +0100 Subject: kbuild: disable clang's default use of -fmerge-all-constants From: Daniel Borkmann <daniel(a)iogearbox.net> commit 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79 upstream. Prasad reported that he has seen crashes in BPF subsystem with netd on Android with arm64 in the form of (note, the taint is unrelated): [ 4134.721483] Unable to handle kernel paging request at virtual address 800000001 [ 4134.820925] Mem abort info: [ 4134.901283] Exception class = DABT (current EL), IL = 32 bits [ 4135.016736] SET = 0, FnV = 0 [ 4135.119820] EA = 0, S1PTW = 0 [ 4135.201431] Data abort info: [ 4135.301388] ISV = 0, ISS = 0x00000021 [ 4135.359599] CM = 0, WnR = 0 [ 4135.470873] user pgtable: 4k pages, 39-bit VAs, pgd = ffffffe39b946000 [ 4135.499757] [0000000800000001] *pgd=0000000000000000, *pud=0000000000000000 [ 4135.660725] Internal error: Oops: 96000021 [#1] PREEMPT SMP [ 4135.674610] Modules linked in: [ 4135.682883] CPU: 5 PID: 1260 Comm: netd Tainted: G S W 4.14.19+ #1 [ 4135.716188] task: ffffffe39f4aa380 task.stack: ffffff801d4e0000 [ 4135.731599] PC is at bpf_prog_add+0x20/0x68 [ 4135.741746] LR is at bpf_prog_inc+0x20/0x2c [ 4135.751788] pc : [<ffffff94ab7ad584>] lr : [<ffffff94ab7ad638>] pstate: 60400145 [ 4135.769062] sp : ffffff801d4e3ce0 [...] [ 4136.258315] Process netd (pid: 1260, stack limit = 0xffffff801d4e0000) [ 4136.273746] Call trace: [...] [ 4136.442494] 3ca0: ffffff94ab7ad584 0000000060400145 ffffffe3a01bf8f8 0000000000000006 [ 4136.460936] 3cc0: 0000008000000000 ffffff94ab844204 ffffff801d4e3cf0 ffffff94ab7ad584 [ 4136.479241] [<ffffff94ab7ad584>] bpf_prog_add+0x20/0x68 [ 4136.491767] [<ffffff94ab7ad638>] bpf_prog_inc+0x20/0x2c [ 4136.504536] [<ffffff94ab7b5d08>] bpf_obj_get_user+0x204/0x22c [ 4136.518746] [<ffffff94ab7ade68>] SyS_bpf+0x5a8/0x1a88 Android's netd was basically pinning the uid cookie BPF map in BPF fs (/sys/fs/bpf/traffic_cookie_uid_map) and later on retrieving it again resulting in above panic. Issue is that the map was wrongly identified as a prog! Above kernel was compiled with clang 4.0, and it turns out that clang decided to merge the bpf_prog_iops and bpf_map_iops into a single memory location, such that the two i_ops could then not be distinguished anymore. Reason for this miscompilation is that clang has the more aggressive -fmerge-all-constants enabled by default. In fact, clang source code has a comment about it in lib/AST/ExprConstant.cpp on why it is okay to do so: Pointers with different bases cannot represent the same object. (Note that clang defaults to -fmerge-all-constants, which can lead to inconsistent results for comparisons involving the address of a constant; this generally doesn't matter in practice.) The issue never appeared with gcc however, since gcc does not enable -fmerge-all-constants by default and even *explicitly* states in it's option description that using this flag results in non-conforming behavior, quote from man gcc: Languages like C or C++ require each variable, including multiple instances of the same variable in recursive calls, to have distinct locations, so using this option results in non-conforming behavior. There are also various clang bug reports open on that matter [1], where clang developers acknowledge the non-conforming behavior, and refer to disabling it with -fno-merge-all-constants. But even if this gets fixed in clang today, there are already users out there that triggered this. Thus, fix this issue by explicitly adding -fno-merge-all-constants to the kernel's Makefile to generically disable this optimization, since potentially other places in the kernel could subtly break as well. Note, there is also a flag called -fmerge-constants (not supported by clang), which is more conservative and only applies to strings and it's enabled in gcc's -O/-O2/-O3/-Os optimization levels. In gcc's code, the two flags -fmerge-{all-,}constants share the same variable internally, so when disabling it via -fno-merge-all-constants, then we really don't merge any const data (e.g. strings), and text size increases with gcc (14,927,214 -> 14,942,646 for vmlinux.o). $ gcc -fverbose-asm -O2 foo.c -S -o foo.S -> foo.S lists -fmerge-constants under options enabled $ gcc -fverbose-asm -O2 -fno-merge-all-constants foo.c -S -o foo.S -> foo.S doesn't list -fmerge-constants under options enabled $ gcc -fverbose-asm -O2 -fno-merge-all-constants -fmerge-constants foo.c -S -o foo.S -> foo.S lists -fmerge-constants under options enabled Thus, as a workaround we need to set both -fno-merge-all-constants *and* -fmerge-constants in the Makefile in order for text size to stay as is. [1] https://bugs.llvm.org/show_bug.cgi?id=18538 Reported-by: Prasad Sodagudi <psodagud(a)codeaurora.org> Signed-off-by: Daniel Borkmann <daniel(a)iogearbox.net> Cc: Linus Torvalds <torvalds(a)linux-foundation.org> Cc: Chenbo Feng <fengc(a)google.com> Cc: Richard Smith <richard-llvm(a)metafoo.co.uk> Cc: Chandler Carruth <chandlerc(a)gmail.com> Cc: linux-kernel(a)vger.kernel.org Tested-by: Prasad Sodagudi <psodagud(a)codeaurora.org> Acked-by: Alexei Starovoitov <ast(a)kernel.org> Signed-off-by: Alexei Starovoitov <ast(a)kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- Makefile | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/Makefile +++ b/Makefile @@ -784,6 +784,15 @@ KBUILD_CFLAGS += $(call cc-disable-warni # disable invalid "can't wrap" optimizations for signed / pointers KBUILD_CFLAGS += $(call cc-option,-fno-strict-overflow) +# clang sets -fmerge-all-constants by default as optimization, but this +# is non-conforming behavior for C and in fact breaks the kernel, so we +# need to disable it here generally. +KBUILD_CFLAGS += $(call cc-option,-fno-merge-all-constants) + +# for gcc -fno-merge-all-constants disables everything, but it is fine +# to have actual conforming behavior enabled. +KBUILD_CFLAGS += $(call cc-option,-fmerge-constants) + # Make sure -fstack-check isn't enabled (like gentoo apparently did) KBUILD_CFLAGS += $(call cc-option,-fno-stack-check,) Patches currently in stable-queue which might be from daniel(a)iogearbox.net are queue-4.4/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch queue-4.4/bpf-skip-unnecessary-capability-check.patch queue-4.4/bpf-x64-increase-number-of-passes.patch

7 years, 8 months

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Patch "bpf, x64: increase number of passes" has been added to the 4.4-stable tree

by gregkh＠linuxfoundation.org

This is a note to let you know that I've just added the patch titled bpf, x64: increase number of passes to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=sum… The filename of the patch is: bpf-x64-increase-number-of-passes.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable(a)vger.kernel.org> know about it. >From 6007b080d2e2adb7af22bf29165f0594ea12b34c Mon Sep 17 00:00:00 2001 From: Daniel Borkmann <daniel(a)iogearbox.net> Date: Wed, 7 Mar 2018 22:10:01 +0100 Subject: bpf, x64: increase number of passes From: Daniel Borkmann <daniel(a)iogearbox.net> commit 6007b080d2e2adb7af22bf29165f0594ea12b34c upstream. In Cilium some of the main programs we run today are hitting 9 passes on x64's JIT compiler, and we've had cases already where we surpassed the limit where the JIT then punts the program to the interpreter instead, leading to insertion failures due to CONFIG_BPF_JIT_ALWAYS_ON or insertion failures due to the prog array owner being JITed but the program to insert not (both must have the same JITed/non-JITed property). One concrete case the program image shrunk from 12,767 bytes down to 10,288 bytes where the image converged after 16 steps. I've measured that this took 340us in the JIT until it converges on my i7-6600U. Thus, increase the original limit we had from day one where the JIT covered cBPF only back then before we run into the case (as similar with the complexity limit) where we trip over this and hit program rejections. Also add a cond_resched() into the compilation loop, the JIT process runs without any locks and may sleep anyway. Signed-off-by: Daniel Borkmann <daniel(a)iogearbox.net> Acked-by: Alexei Starovoitov <ast(a)kernel.org> Reviewed-by: Eric Dumazet <edumazet(a)google.com> Signed-off-by: Alexei Starovoitov <ast(a)kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- arch/x86/net/bpf_jit_comp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1077,7 +1077,7 @@ void bpf_int_jit_compile(struct bpf_prog * may converge on the last pass. In such case do one more * pass to emit the final image */ - for (pass = 0; pass < 10 || image; pass++) { + for (pass = 0; pass < 20 || image; pass++) { proglen = do_jit(prog, addrs, image, oldproglen, &ctx); if (proglen <= 0) { image = NULL; @@ -1100,6 +1100,7 @@ void bpf_int_jit_compile(struct bpf_prog goto out; } oldproglen = proglen; + cond_resched(); } if (bpf_jit_enable > 1) Patches currently in stable-queue which might be from daniel(a)iogearbox.net are queue-4.4/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch queue-4.4/bpf-skip-unnecessary-capability-check.patch queue-4.4/bpf-x64-increase-number-of-passes.patch

7 years, 8 months

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Patch "bpf: skip unnecessary capability check" has been added to the 4.4-stable tree

by gregkh＠linuxfoundation.org

This is a note to let you know that I've just added the patch titled bpf: skip unnecessary capability check to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=sum… The filename of the patch is: bpf-skip-unnecessary-capability-check.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable(a)vger.kernel.org> know about it. >From 0fa4fe85f4724fff89b09741c437cbee9cf8b008 Mon Sep 17 00:00:00 2001 From: Chenbo Feng <fengc(a)google.com> Date: Mon, 19 Mar 2018 17:57:27 -0700 Subject: bpf: skip unnecessary capability check From: Chenbo Feng <fengc(a)google.com> commit 0fa4fe85f4724fff89b09741c437cbee9cf8b008 upstream. The current check statement in BPF syscall will do a capability check for CAP_SYS_ADMIN before checking sysctl_unprivileged_bpf_disabled. This code path will trigger unnecessary security hooks on capability checking and cause false alarms on unprivileged process trying to get CAP_SYS_ADMIN access. This can be resolved by simply switch the order of the statement and CAP_SYS_ADMIN is not required anyway if unprivileged bpf syscall is allowed. Signed-off-by: Chenbo Feng <fengc(a)google.com> Acked-by: Lorenzo Colitti <lorenzo(a)google.com> Signed-off-by: Daniel Borkmann <daniel(a)iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- kernel/bpf/syscall.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -673,7 +673,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf union bpf_attr attr = {}; int err; - if (!capable(CAP_SYS_ADMIN) && sysctl_unprivileged_bpf_disabled) + if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN)) return -EPERM; if (!access_ok(VERIFY_READ, uattr, 1)) Patches currently in stable-queue which might be from fengc(a)google.com are queue-4.4/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch queue-4.4/bpf-skip-unnecessary-capability-check.patch

7 years, 8 months

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Patch "kbuild: disable clang's default use of -fmerge-all-constants" has been added to the 4.15-stable tree

by gregkh＠linuxfoundation.org

This is a note to let you know that I've just added the patch titled kbuild: disable clang's default use of -fmerge-all-constants to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=sum… The filename of the patch is: kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch and it can be found in the queue-4.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable(a)vger.kernel.org> know about it. >From 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann <daniel(a)iogearbox.net> Date: Wed, 21 Mar 2018 01:18:24 +0100 Subject: kbuild: disable clang's default use of -fmerge-all-constants From: Daniel Borkmann <daniel(a)iogearbox.net> commit 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79 upstream. Prasad reported that he has seen crashes in BPF subsystem with netd on Android with arm64 in the form of (note, the taint is unrelated): [ 4134.721483] Unable to handle kernel paging request at virtual address 800000001 [ 4134.820925] Mem abort info: [ 4134.901283] Exception class = DABT (current EL), IL = 32 bits [ 4135.016736] SET = 0, FnV = 0 [ 4135.119820] EA = 0, S1PTW = 0 [ 4135.201431] Data abort info: [ 4135.301388] ISV = 0, ISS = 0x00000021 [ 4135.359599] CM = 0, WnR = 0 [ 4135.470873] user pgtable: 4k pages, 39-bit VAs, pgd = ffffffe39b946000 [ 4135.499757] [0000000800000001] *pgd=0000000000000000, *pud=0000000000000000 [ 4135.660725] Internal error: Oops: 96000021 [#1] PREEMPT SMP [ 4135.674610] Modules linked in: [ 4135.682883] CPU: 5 PID: 1260 Comm: netd Tainted: G S W 4.14.19+ #1 [ 4135.716188] task: ffffffe39f4aa380 task.stack: ffffff801d4e0000 [ 4135.731599] PC is at bpf_prog_add+0x20/0x68 [ 4135.741746] LR is at bpf_prog_inc+0x20/0x2c [ 4135.751788] pc : [<ffffff94ab7ad584>] lr : [<ffffff94ab7ad638>] pstate: 60400145 [ 4135.769062] sp : ffffff801d4e3ce0 [...] [ 4136.258315] Process netd (pid: 1260, stack limit = 0xffffff801d4e0000) [ 4136.273746] Call trace: [...] [ 4136.442494] 3ca0: ffffff94ab7ad584 0000000060400145 ffffffe3a01bf8f8 0000000000000006 [ 4136.460936] 3cc0: 0000008000000000 ffffff94ab844204 ffffff801d4e3cf0 ffffff94ab7ad584 [ 4136.479241] [<ffffff94ab7ad584>] bpf_prog_add+0x20/0x68 [ 4136.491767] [<ffffff94ab7ad638>] bpf_prog_inc+0x20/0x2c [ 4136.504536] [<ffffff94ab7b5d08>] bpf_obj_get_user+0x204/0x22c [ 4136.518746] [<ffffff94ab7ade68>] SyS_bpf+0x5a8/0x1a88 Android's netd was basically pinning the uid cookie BPF map in BPF fs (/sys/fs/bpf/traffic_cookie_uid_map) and later on retrieving it again resulting in above panic. Issue is that the map was wrongly identified as a prog! Above kernel was compiled with clang 4.0, and it turns out that clang decided to merge the bpf_prog_iops and bpf_map_iops into a single memory location, such that the two i_ops could then not be distinguished anymore. Reason for this miscompilation is that clang has the more aggressive -fmerge-all-constants enabled by default. In fact, clang source code has a comment about it in lib/AST/ExprConstant.cpp on why it is okay to do so: Pointers with different bases cannot represent the same object. (Note that clang defaults to -fmerge-all-constants, which can lead to inconsistent results for comparisons involving the address of a constant; this generally doesn't matter in practice.) The issue never appeared with gcc however, since gcc does not enable -fmerge-all-constants by default and even *explicitly* states in it's option description that using this flag results in non-conforming behavior, quote from man gcc: Languages like C or C++ require each variable, including multiple instances of the same variable in recursive calls, to have distinct locations, so using this option results in non-conforming behavior. There are also various clang bug reports open on that matter [1], where clang developers acknowledge the non-conforming behavior, and refer to disabling it with -fno-merge-all-constants. But even if this gets fixed in clang today, there are already users out there that triggered this. Thus, fix this issue by explicitly adding -fno-merge-all-constants to the kernel's Makefile to generically disable this optimization, since potentially other places in the kernel could subtly break as well. Note, there is also a flag called -fmerge-constants (not supported by clang), which is more conservative and only applies to strings and it's enabled in gcc's -O/-O2/-O3/-Os optimization levels. In gcc's code, the two flags -fmerge-{all-,}constants share the same variable internally, so when disabling it via -fno-merge-all-constants, then we really don't merge any const data (e.g. strings), and text size increases with gcc (14,927,214 -> 14,942,646 for vmlinux.o). $ gcc -fverbose-asm -O2 foo.c -S -o foo.S -> foo.S lists -fmerge-constants under options enabled $ gcc -fverbose-asm -O2 -fno-merge-all-constants foo.c -S -o foo.S -> foo.S doesn't list -fmerge-constants under options enabled $ gcc -fverbose-asm -O2 -fno-merge-all-constants -fmerge-constants foo.c -S -o foo.S -> foo.S lists -fmerge-constants under options enabled Thus, as a workaround we need to set both -fno-merge-all-constants *and* -fmerge-constants in the Makefile in order for text size to stay as is. [1] https://bugs.llvm.org/show_bug.cgi?id=18538 Reported-by: Prasad Sodagudi <psodagud(a)codeaurora.org> Signed-off-by: Daniel Borkmann <daniel(a)iogearbox.net> Cc: Linus Torvalds <torvalds(a)linux-foundation.org> Cc: Chenbo Feng <fengc(a)google.com> Cc: Richard Smith <richard-llvm(a)metafoo.co.uk> Cc: Chandler Carruth <chandlerc(a)gmail.com> Cc: linux-kernel(a)vger.kernel.org Tested-by: Prasad Sodagudi <psodagud(a)codeaurora.org> Acked-by: Alexei Starovoitov <ast(a)kernel.org> Signed-off-by: Alexei Starovoitov <ast(a)kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- Makefile | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/Makefile +++ b/Makefile @@ -798,6 +798,15 @@ KBUILD_CFLAGS += $(call cc-disable-warni # disable invalid "can't wrap" optimizations for signed / pointers KBUILD_CFLAGS += $(call cc-option,-fno-strict-overflow) +# clang sets -fmerge-all-constants by default as optimization, but this +# is non-conforming behavior for C and in fact breaks the kernel, so we +# need to disable it here generally. +KBUILD_CFLAGS += $(call cc-option,-fno-merge-all-constants) + +# for gcc -fno-merge-all-constants disables everything, but it is fine +# to have actual conforming behavior enabled. +KBUILD_CFLAGS += $(call cc-option,-fmerge-constants) + # Make sure -fstack-check isn't enabled (like gentoo apparently did) KBUILD_CFLAGS += $(call cc-option,-fno-stack-check,) Patches currently in stable-queue which might be from daniel(a)iogearbox.net are queue-4.15/trace-bpf-remove-helper-bpf_perf_prog_read_value-from-tracepoint-type-programs.patch queue-4.15/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch queue-4.15/bpf-skip-unnecessary-capability-check.patch queue-4.15/bpf-x64-increase-number-of-passes.patch

7 years, 8 months

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Patch "bpf, x64: increase number of passes" has been added to the 4.15-stable tree

by gregkh＠linuxfoundation.org

This is a note to let you know that I've just added the patch titled bpf, x64: increase number of passes to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=sum… The filename of the patch is: bpf-x64-increase-number-of-passes.patch and it can be found in the queue-4.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable(a)vger.kernel.org> know about it. >From 6007b080d2e2adb7af22bf29165f0594ea12b34c Mon Sep 17 00:00:00 2001 From: Daniel Borkmann <daniel(a)iogearbox.net> Date: Wed, 7 Mar 2018 22:10:01 +0100 Subject: bpf, x64: increase number of passes From: Daniel Borkmann <daniel(a)iogearbox.net> commit 6007b080d2e2adb7af22bf29165f0594ea12b34c upstream. In Cilium some of the main programs we run today are hitting 9 passes on x64's JIT compiler, and we've had cases already where we surpassed the limit where the JIT then punts the program to the interpreter instead, leading to insertion failures due to CONFIG_BPF_JIT_ALWAYS_ON or insertion failures due to the prog array owner being JITed but the program to insert not (both must have the same JITed/non-JITed property). One concrete case the program image shrunk from 12,767 bytes down to 10,288 bytes where the image converged after 16 steps. I've measured that this took 340us in the JIT until it converges on my i7-6600U. Thus, increase the original limit we had from day one where the JIT covered cBPF only back then before we run into the case (as similar with the complexity limit) where we trip over this and hit program rejections. Also add a cond_resched() into the compilation loop, the JIT process runs without any locks and may sleep anyway. Signed-off-by: Daniel Borkmann <daniel(a)iogearbox.net> Acked-by: Alexei Starovoitov <ast(a)kernel.org> Reviewed-by: Eric Dumazet <edumazet(a)google.com> Signed-off-by: Alexei Starovoitov <ast(a)kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- arch/x86/net/bpf_jit_comp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1156,7 +1156,7 @@ struct bpf_prog *bpf_int_jit_compile(str * may converge on the last pass. In such case do one more * pass to emit the final image */ - for (pass = 0; pass < 10 || image; pass++) { + for (pass = 0; pass < 20 || image; pass++) { proglen = do_jit(prog, addrs, image, oldproglen, &ctx); if (proglen <= 0) { image = NULL; @@ -1183,6 +1183,7 @@ struct bpf_prog *bpf_int_jit_compile(str } } oldproglen = proglen; + cond_resched(); } if (bpf_jit_enable > 1) Patches currently in stable-queue which might be from daniel(a)iogearbox.net are queue-4.15/trace-bpf-remove-helper-bpf_perf_prog_read_value-from-tracepoint-type-programs.patch queue-4.15/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch queue-4.15/bpf-skip-unnecessary-capability-check.patch queue-4.15/bpf-x64-increase-number-of-passes.patch

7 years, 8 months

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Patch "bpf: skip unnecessary capability check" has been added to the 4.15-stable tree

by gregkh＠linuxfoundation.org

This is a note to let you know that I've just added the patch titled bpf: skip unnecessary capability check to the 4.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=sum… The filename of the patch is: bpf-skip-unnecessary-capability-check.patch and it can be found in the queue-4.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable(a)vger.kernel.org> know about it. >From 0fa4fe85f4724fff89b09741c437cbee9cf8b008 Mon Sep 17 00:00:00 2001 From: Chenbo Feng <fengc(a)google.com> Date: Mon, 19 Mar 2018 17:57:27 -0700 Subject: bpf: skip unnecessary capability check From: Chenbo Feng <fengc(a)google.com> commit 0fa4fe85f4724fff89b09741c437cbee9cf8b008 upstream. The current check statement in BPF syscall will do a capability check for CAP_SYS_ADMIN before checking sysctl_unprivileged_bpf_disabled. This code path will trigger unnecessary security hooks on capability checking and cause false alarms on unprivileged process trying to get CAP_SYS_ADMIN access. This can be resolved by simply switch the order of the statement and CAP_SYS_ADMIN is not required anyway if unprivileged bpf syscall is allowed. Signed-off-by: Chenbo Feng <fengc(a)google.com> Acked-by: Lorenzo Colitti <lorenzo(a)google.com> Signed-off-by: Daniel Borkmann <daniel(a)iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- kernel/bpf/syscall.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1687,7 +1687,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf union bpf_attr attr = {}; int err; - if (!capable(CAP_SYS_ADMIN) && sysctl_unprivileged_bpf_disabled) + if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN)) return -EPERM; err = check_uarg_tail_zero(uattr, sizeof(attr), size); Patches currently in stable-queue which might be from fengc(a)google.com are queue-4.15/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch queue-4.15/bpf-skip-unnecessary-capability-check.patch

7 years, 8 months

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Patch "kbuild: disable clang's default use of -fmerge-all-constants" has been added to the 4.14-stable tree

by gregkh＠linuxfoundation.org

This is a note to let you know that I've just added the patch titled kbuild: disable clang's default use of -fmerge-all-constants to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=sum… The filename of the patch is: kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable(a)vger.kernel.org> know about it. >From 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann <daniel(a)iogearbox.net> Date: Wed, 21 Mar 2018 01:18:24 +0100 Subject: kbuild: disable clang's default use of -fmerge-all-constants From: Daniel Borkmann <daniel(a)iogearbox.net> commit 87e0d4f0f37fb0c8c4aeeac46fff5e957738df79 upstream. Prasad reported that he has seen crashes in BPF subsystem with netd on Android with arm64 in the form of (note, the taint is unrelated): [ 4134.721483] Unable to handle kernel paging request at virtual address 800000001 [ 4134.820925] Mem abort info: [ 4134.901283] Exception class = DABT (current EL), IL = 32 bits [ 4135.016736] SET = 0, FnV = 0 [ 4135.119820] EA = 0, S1PTW = 0 [ 4135.201431] Data abort info: [ 4135.301388] ISV = 0, ISS = 0x00000021 [ 4135.359599] CM = 0, WnR = 0 [ 4135.470873] user pgtable: 4k pages, 39-bit VAs, pgd = ffffffe39b946000 [ 4135.499757] [0000000800000001] *pgd=0000000000000000, *pud=0000000000000000 [ 4135.660725] Internal error: Oops: 96000021 [#1] PREEMPT SMP [ 4135.674610] Modules linked in: [ 4135.682883] CPU: 5 PID: 1260 Comm: netd Tainted: G S W 4.14.19+ #1 [ 4135.716188] task: ffffffe39f4aa380 task.stack: ffffff801d4e0000 [ 4135.731599] PC is at bpf_prog_add+0x20/0x68 [ 4135.741746] LR is at bpf_prog_inc+0x20/0x2c [ 4135.751788] pc : [<ffffff94ab7ad584>] lr : [<ffffff94ab7ad638>] pstate: 60400145 [ 4135.769062] sp : ffffff801d4e3ce0 [...] [ 4136.258315] Process netd (pid: 1260, stack limit = 0xffffff801d4e0000) [ 4136.273746] Call trace: [...] [ 4136.442494] 3ca0: ffffff94ab7ad584 0000000060400145 ffffffe3a01bf8f8 0000000000000006 [ 4136.460936] 3cc0: 0000008000000000 ffffff94ab844204 ffffff801d4e3cf0 ffffff94ab7ad584 [ 4136.479241] [<ffffff94ab7ad584>] bpf_prog_add+0x20/0x68 [ 4136.491767] [<ffffff94ab7ad638>] bpf_prog_inc+0x20/0x2c [ 4136.504536] [<ffffff94ab7b5d08>] bpf_obj_get_user+0x204/0x22c [ 4136.518746] [<ffffff94ab7ade68>] SyS_bpf+0x5a8/0x1a88 Android's netd was basically pinning the uid cookie BPF map in BPF fs (/sys/fs/bpf/traffic_cookie_uid_map) and later on retrieving it again resulting in above panic. Issue is that the map was wrongly identified as a prog! Above kernel was compiled with clang 4.0, and it turns out that clang decided to merge the bpf_prog_iops and bpf_map_iops into a single memory location, such that the two i_ops could then not be distinguished anymore. Reason for this miscompilation is that clang has the more aggressive -fmerge-all-constants enabled by default. In fact, clang source code has a comment about it in lib/AST/ExprConstant.cpp on why it is okay to do so: Pointers with different bases cannot represent the same object. (Note that clang defaults to -fmerge-all-constants, which can lead to inconsistent results for comparisons involving the address of a constant; this generally doesn't matter in practice.) The issue never appeared with gcc however, since gcc does not enable -fmerge-all-constants by default and even *explicitly* states in it's option description that using this flag results in non-conforming behavior, quote from man gcc: Languages like C or C++ require each variable, including multiple instances of the same variable in recursive calls, to have distinct locations, so using this option results in non-conforming behavior. There are also various clang bug reports open on that matter [1], where clang developers acknowledge the non-conforming behavior, and refer to disabling it with -fno-merge-all-constants. But even if this gets fixed in clang today, there are already users out there that triggered this. Thus, fix this issue by explicitly adding -fno-merge-all-constants to the kernel's Makefile to generically disable this optimization, since potentially other places in the kernel could subtly break as well. Note, there is also a flag called -fmerge-constants (not supported by clang), which is more conservative and only applies to strings and it's enabled in gcc's -O/-O2/-O3/-Os optimization levels. In gcc's code, the two flags -fmerge-{all-,}constants share the same variable internally, so when disabling it via -fno-merge-all-constants, then we really don't merge any const data (e.g. strings), and text size increases with gcc (14,927,214 -> 14,942,646 for vmlinux.o). $ gcc -fverbose-asm -O2 foo.c -S -o foo.S -> foo.S lists -fmerge-constants under options enabled $ gcc -fverbose-asm -O2 -fno-merge-all-constants foo.c -S -o foo.S -> foo.S doesn't list -fmerge-constants under options enabled $ gcc -fverbose-asm -O2 -fno-merge-all-constants -fmerge-constants foo.c -S -o foo.S -> foo.S lists -fmerge-constants under options enabled Thus, as a workaround we need to set both -fno-merge-all-constants *and* -fmerge-constants in the Makefile in order for text size to stay as is. [1] https://bugs.llvm.org/show_bug.cgi?id=18538 Reported-by: Prasad Sodagudi <psodagud(a)codeaurora.org> Signed-off-by: Daniel Borkmann <daniel(a)iogearbox.net> Cc: Linus Torvalds <torvalds(a)linux-foundation.org> Cc: Chenbo Feng <fengc(a)google.com> Cc: Richard Smith <richard-llvm(a)metafoo.co.uk> Cc: Chandler Carruth <chandlerc(a)gmail.com> Cc: linux-kernel(a)vger.kernel.org Tested-by: Prasad Sodagudi <psodagud(a)codeaurora.org> Acked-by: Alexei Starovoitov <ast(a)kernel.org> Signed-off-by: Alexei Starovoitov <ast(a)kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- Makefile | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/Makefile +++ b/Makefile @@ -805,6 +805,15 @@ KBUILD_CFLAGS += $(call cc-disable-warni # disable invalid "can't wrap" optimizations for signed / pointers KBUILD_CFLAGS += $(call cc-option,-fno-strict-overflow) +# clang sets -fmerge-all-constants by default as optimization, but this +# is non-conforming behavior for C and in fact breaks the kernel, so we +# need to disable it here generally. +KBUILD_CFLAGS += $(call cc-option,-fno-merge-all-constants) + +# for gcc -fno-merge-all-constants disables everything, but it is fine +# to have actual conforming behavior enabled. +KBUILD_CFLAGS += $(call cc-option,-fmerge-constants) + # Make sure -fstack-check isn't enabled (like gentoo apparently did) KBUILD_CFLAGS += $(call cc-option,-fno-stack-check,) Patches currently in stable-queue which might be from daniel(a)iogearbox.net are queue-4.14/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch queue-4.14/bpf-skip-unnecessary-capability-check.patch queue-4.14/bpf-x64-increase-number-of-passes.patch

7 years, 8 months

1
0
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Patch "bpf, x64: increase number of passes" has been added to the 4.14-stable tree

by gregkh＠linuxfoundation.org

This is a note to let you know that I've just added the patch titled bpf, x64: increase number of passes to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=sum… The filename of the patch is: bpf-x64-increase-number-of-passes.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable(a)vger.kernel.org> know about it. >From 6007b080d2e2adb7af22bf29165f0594ea12b34c Mon Sep 17 00:00:00 2001 From: Daniel Borkmann <daniel(a)iogearbox.net> Date: Wed, 7 Mar 2018 22:10:01 +0100 Subject: bpf, x64: increase number of passes From: Daniel Borkmann <daniel(a)iogearbox.net> commit 6007b080d2e2adb7af22bf29165f0594ea12b34c upstream. In Cilium some of the main programs we run today are hitting 9 passes on x64's JIT compiler, and we've had cases already where we surpassed the limit where the JIT then punts the program to the interpreter instead, leading to insertion failures due to CONFIG_BPF_JIT_ALWAYS_ON or insertion failures due to the prog array owner being JITed but the program to insert not (both must have the same JITed/non-JITed property). One concrete case the program image shrunk from 12,767 bytes down to 10,288 bytes where the image converged after 16 steps. I've measured that this took 340us in the JIT until it converges on my i7-6600U. Thus, increase the original limit we had from day one where the JIT covered cBPF only back then before we run into the case (as similar with the complexity limit) where we trip over this and hit program rejections. Also add a cond_resched() into the compilation loop, the JIT process runs without any locks and may sleep anyway. Signed-off-by: Daniel Borkmann <daniel(a)iogearbox.net> Acked-by: Alexei Starovoitov <ast(a)kernel.org> Reviewed-by: Eric Dumazet <edumazet(a)google.com> Signed-off-by: Alexei Starovoitov <ast(a)kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- arch/x86/net/bpf_jit_comp.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1156,7 +1156,7 @@ struct bpf_prog *bpf_int_jit_compile(str * may converge on the last pass. In such case do one more * pass to emit the final image */ - for (pass = 0; pass < 10 || image; pass++) { + for (pass = 0; pass < 20 || image; pass++) { proglen = do_jit(prog, addrs, image, oldproglen, &ctx); if (proglen <= 0) { image = NULL; @@ -1183,6 +1183,7 @@ struct bpf_prog *bpf_int_jit_compile(str } } oldproglen = proglen; + cond_resched(); } if (bpf_jit_enable > 1) Patches currently in stable-queue which might be from daniel(a)iogearbox.net are queue-4.14/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch queue-4.14/bpf-skip-unnecessary-capability-check.patch queue-4.14/bpf-x64-increase-number-of-passes.patch

7 years, 8 months

1
0
0 0

Patch "bpf: skip unnecessary capability check" has been added to the 4.14-stable tree

by gregkh＠linuxfoundation.org

This is a note to let you know that I've just added the patch titled bpf: skip unnecessary capability check to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=sum… The filename of the patch is: bpf-skip-unnecessary-capability-check.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable(a)vger.kernel.org> know about it. >From 0fa4fe85f4724fff89b09741c437cbee9cf8b008 Mon Sep 17 00:00:00 2001 From: Chenbo Feng <fengc(a)google.com> Date: Mon, 19 Mar 2018 17:57:27 -0700 Subject: bpf: skip unnecessary capability check From: Chenbo Feng <fengc(a)google.com> commit 0fa4fe85f4724fff89b09741c437cbee9cf8b008 upstream. The current check statement in BPF syscall will do a capability check for CAP_SYS_ADMIN before checking sysctl_unprivileged_bpf_disabled. This code path will trigger unnecessary security hooks on capability checking and cause false alarms on unprivileged process trying to get CAP_SYS_ADMIN access. This can be resolved by simply switch the order of the statement and CAP_SYS_ADMIN is not required anyway if unprivileged bpf syscall is allowed. Signed-off-by: Chenbo Feng <fengc(a)google.com> Acked-by: Lorenzo Colitti <lorenzo(a)google.com> Signed-off-by: Daniel Borkmann <daniel(a)iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> --- kernel/bpf/syscall.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1455,7 +1455,7 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf union bpf_attr attr = {}; int err; - if (!capable(CAP_SYS_ADMIN) && sysctl_unprivileged_bpf_disabled) + if (sysctl_unprivileged_bpf_disabled && !capable(CAP_SYS_ADMIN)) return -EPERM; err = check_uarg_tail_zero(uattr, sizeof(attr), size); Patches currently in stable-queue which might be from fengc(a)google.com are queue-4.14/kbuild-disable-clang-s-default-use-of-fmerge-all-constants.patch queue-4.14/bpf-skip-unnecessary-capability-check.patch

7 years, 8 months

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