`MFD_NOEXEC_SEAL` should remove the executable bits and set `F_SEAL_EXEC`
to prevent further modifications to the executable bits as per the comment
in the uapi header file:
not executable and sealed to prevent changing to executable
However, commit 105ff5339f498a ("mm/memfd: add MFD_NOEXEC_SEAL and MFD_EXEC")
that introduced this feature made it so that `MFD_NOEXEC_SEAL` unsets
`F_SEAL_SEAL`, essentially acting as a superset of `MFD_ALLOW_SEALING`.
Nothing implies that it should be so, and indeed up until the second version
of the of the patchset[0] that introduced `MFD_EXEC` and `MFD_NOEXEC_SEAL`,
`F_SEAL_SEAL` was not removed, however, it was changed in the third revision
of the patchset[1] without a clear explanation.
This behaviour is surprising for application developers, there is no
documentation that would reveal that `MFD_NOEXEC_SEAL` has the additional
effect of `MFD_ALLOW_SEALING`. Additionally, combined with `vm.memfd_noexec=2`
it has the effect of making all memfds initially sealable.
So do not remove `F_SEAL_SEAL` when `MFD_NOEXEC_SEAL` is requested,
thereby returning to the pre-Linux 6.3 behaviour of only allowing
sealing when `MFD_ALLOW_SEALING` is specified.
Now, this is technically a uapi break. However, the damage is expected
to be minimal. To trigger user visible change, a program has to do the
following steps:
- create memfd:
- with `MFD_NOEXEC_SEAL`,
- without `MFD_ALLOW_SEALING`;
- try to add seals / check the seals.
But that seems unlikely to happen intentionally since this change
essentially reverts the kernel's behaviour to that of Linux <6.3,
so if a program worked correctly on those older kernels, it will
likely work correctly after this change.
I have used Debian Code Search and GitHub to try to find potential
breakages, and I could only find a single one. dbus-broker's
memfd_create() wrapper is aware of this implicit `MFD_ALLOW_SEALING`
behaviour, and tries to work around it[2]. This workaround will
break. Luckily, this only affects the test suite, it does not affect
the normal operations of dbus-broker. There is a PR with a fix[3].
I also carried out a smoke test by building a kernel with this change
and booting an Arch Linux system into GNOME and Plasma sessions.
There was also a previous attempt to address this peculiarity by
introducing a new flag[4].
[0]: https://lore.kernel.org/lkml/20220805222126.142525-3-jeffxu@google.com/
[1]: https://lore.kernel.org/lkml/20221202013404.163143-3-jeffxu@google.com/
[2]: https://github.com/bus1/dbus-broker/blob/9eb0b7e5826fc76cad7b025bc46f267d4a…
[3]: https://github.com/bus1/dbus-broker/pull/366
[4]: https://lore.kernel.org/lkml/20230714114753.170814-1-david@readahead.eu/
Cc: stable(a)vger.kernel.org
Signed-off-by: Barnabás Pőcze <pobrn(a)protonmail.com>
---
* v3: https://lore.kernel.org/linux-mm/20240611231409.3899809-1-jeffxu@chromium.o…
* v2: https://lore.kernel.org/linux-mm/20240524033933.135049-1-jeffxu@google.com/
* v1: https://lore.kernel.org/linux-mm/20240513191544.94754-1-pobrn@protonmail.co…
This fourth version returns to removing the inconsistency as opposed to documenting
its existence, with the same code change as v1 but with a somewhat extended commit
message. This is sent because I believe it is worth at least a try; it can be easily
reverted if bigger application breakages are discovered than initially imagined.
---
mm/memfd.c | 9 ++++-----
tools/testing/selftests/memfd/memfd_test.c | 2 +-
2 files changed, 5 insertions(+), 6 deletions(-)
diff --git a/mm/memfd.c b/mm/memfd.c
index 7d8d3ab3fa37..8b7f6afee21d 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -356,12 +356,11 @@ SYSCALL_DEFINE2(memfd_create,
inode->i_mode &= ~0111;
file_seals = memfd_file_seals_ptr(file);
- if (file_seals) {
- *file_seals &= ~F_SEAL_SEAL;
+ if (file_seals)
*file_seals |= F_SEAL_EXEC;
- }
- } else if (flags & MFD_ALLOW_SEALING) {
- /* MFD_EXEC and MFD_ALLOW_SEALING are set */
+ }
+
+ if (flags & MFD_ALLOW_SEALING) {
file_seals = memfd_file_seals_ptr(file);
if (file_seals)
*file_seals &= ~F_SEAL_SEAL;
diff --git a/tools/testing/selftests/memfd/memfd_test.c b/tools/testing/selftests/memfd/memfd_test.c
index 95af2d78fd31..7b78329f65b6 100644
--- a/tools/testing/selftests/memfd/memfd_test.c
+++ b/tools/testing/selftests/memfd/memfd_test.c
@@ -1151,7 +1151,7 @@ static void test_noexec_seal(void)
mfd_def_size,
MFD_CLOEXEC | MFD_NOEXEC_SEAL);
mfd_assert_mode(fd, 0666);
- mfd_assert_has_seals(fd, F_SEAL_EXEC);
+ mfd_assert_has_seals(fd, F_SEAL_SEAL | F_SEAL_EXEC);
mfd_fail_chmod(fd, 0777);
close(fd);
}
--
2.45.2
SCM driver looks messy in terms of handling concurrency of probe. The
driver exports interface which is guarded by global '__scm' variable
but:
1. Lacks proper read barrier (commit adding write barriers mixed up
READ_ONCE with a read barrier).
2. Lacks barriers or checks for '__scm' in multiple places.
3. Lacks probe error cleanup.
I fixed here few visible things, but this was not tested extensively. I
tried only SM8450.
ARM32 and SC8280xp/X1E platforms would be useful for testing as well.
All the issues here are non-urgent, IOW, they were here for some time
(v6.10-rc1 and earlier).
Best regards,
Krzysztof
---
Krzysztof Kozlowski (6):
firmware: qcom: scm: Fix missing read barrier in qcom_scm_is_available()
firmware: qcom: scm: Fix missing read barrier in qcom_scm_get_tzmem_pool()
firmware: qcom: scm: Handle various probe ordering for qcom_scm_assign_mem()
[RFC/RFT] firmware: qcom: scm: Cleanup global '__scm' on probe failures
firmware: qcom: scm: smc: Handle missing SCM device
firmware: qcom: scm: smc: Narrow 'mempool' variable scope
drivers/firmware/qcom/qcom_scm-smc.c | 6 +++-
drivers/firmware/qcom/qcom_scm.c | 55 +++++++++++++++++++++++++-----------
2 files changed, 44 insertions(+), 17 deletions(-)
---
base-commit: 414c97c966b69e4a6ea7b32970fa166b2f9b9ef0
change-id: 20241119-qcom-scm-missing-barriers-and-all-sort-of-srap-a25d59074882
Best regards,
--
Krzysztof Kozlowski <krzysztof.kozlowski(a)linaro.org>
Some cameras do not return all the bytes requested from a control
if it can fit in less bytes. Eg: returning 0xab instead of 0x00ab.
Support these devices.
Also, now that we are at it, improve uvc_query_ctrl() logging.
Signed-off-by: Ricardo Ribalda <ribalda(a)chromium.org>
---
Changes in v3:
- Improve documentation.
- Do not change return sequence.
- Use dev_ratelimit and dev_warn_once
- Link to v2: https://lore.kernel.org/r/20241008-uvc-readless-v2-0-04d9d51aee56@chromium.…
Changes in v2:
- Rewrite error handling (Thanks Sakari)
- Discard 2/3. It is not needed after rewriting the error handling.
- Link to v1: https://lore.kernel.org/r/20241008-uvc-readless-v1-0-042ac4581f44@chromium.…
---
Ricardo Ribalda (2):
media: uvcvideo: Support partial control reads
media: uvcvideo: Add more logging to uvc_query_ctrl()
drivers/media/usb/uvc/uvc_video.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
---
base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
change-id: 20241008-uvc-readless-23f9b8cad0b3
Best regards,
--
Ricardo Ribalda <ribalda(a)chromium.org>
From: Linus Walleij <linus.walleij(a)linaro.org>
[ Upstream commit 4aea16b7cfb76bd3361858ceee6893ef5c9b5570 ]
When enabling expert mode CONFIG_EXPERT and using that power
user mode to disable the branch prediction hardening
!CONFIG_HARDEN_BRANCH_PREDICTOR, the assembly linker
in CLANG notices that some assembly in proc-v7.S does
not have corresponding C call sites, i.e. the prototypes
in proc-v7-bugs.c are enclosed in ifdef
CONFIG_HARDEN_BRANCH_PREDICTOR so this assembly:
SYM_TYPED_FUNC_START(cpu_v7_smc_switch_mm)
SYM_TYPED_FUNC_START(cpu_v7_hvc_switch_mm)
Results in:
ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_smc_switch_mm
>>> referenced by proc-v7.S:94 (.../arch/arm/mm/proc-v7.S:94)
>>> arch/arm/mm/proc-v7.o:(.text+0x108) in archive vmlinux.a
ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_hvc_switch_mm
>>> referenced by proc-v7.S:105 (.../arch/arm/mm/proc-v7.S:105)
>>> arch/arm/mm/proc-v7.o:(.text+0x124) in archive vmlinux.a
Fix this by adding an additional requirement that
CONFIG_HARDEN_BRANCH_PREDICTOR has to be enabled to compile
these assembly calls.
Closes: https://lore.kernel.org/oe-kbuild-all/202411041456.ZsoEiD7T-lkp@intel.com/
Reported-by: kernel test robot <lkp(a)intel.com>
Reviewed-by: Nathan Chancellor <nathan(a)kernel.org>
Signed-off-by: Linus Walleij <linus.walleij(a)linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel(a)armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal(a)kernel.org>
---
arch/arm/mm/proc-v7.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index e351d682c2e36..8bde80b31a861 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -94,7 +94,7 @@ ENTRY(cpu_v7_dcache_clean_area)
ret lr
ENDPROC(cpu_v7_dcache_clean_area)
-#ifdef CONFIG_ARM_PSCI
+#if defined(CONFIG_ARM_PSCI) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
.arch_extension sec
ENTRY(cpu_v7_smc_switch_mm)
stmfd sp!, {r0 - r3}
--
2.43.0
From: Linus Walleij <linus.walleij(a)linaro.org>
[ Upstream commit 4aea16b7cfb76bd3361858ceee6893ef5c9b5570 ]
When enabling expert mode CONFIG_EXPERT and using that power
user mode to disable the branch prediction hardening
!CONFIG_HARDEN_BRANCH_PREDICTOR, the assembly linker
in CLANG notices that some assembly in proc-v7.S does
not have corresponding C call sites, i.e. the prototypes
in proc-v7-bugs.c are enclosed in ifdef
CONFIG_HARDEN_BRANCH_PREDICTOR so this assembly:
SYM_TYPED_FUNC_START(cpu_v7_smc_switch_mm)
SYM_TYPED_FUNC_START(cpu_v7_hvc_switch_mm)
Results in:
ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_smc_switch_mm
>>> referenced by proc-v7.S:94 (.../arch/arm/mm/proc-v7.S:94)
>>> arch/arm/mm/proc-v7.o:(.text+0x108) in archive vmlinux.a
ld.lld: error: undefined symbol: __kcfi_typeid_cpu_v7_hvc_switch_mm
>>> referenced by proc-v7.S:105 (.../arch/arm/mm/proc-v7.S:105)
>>> arch/arm/mm/proc-v7.o:(.text+0x124) in archive vmlinux.a
Fix this by adding an additional requirement that
CONFIG_HARDEN_BRANCH_PREDICTOR has to be enabled to compile
these assembly calls.
Closes: https://lore.kernel.org/oe-kbuild-all/202411041456.ZsoEiD7T-lkp@intel.com/
Reported-by: kernel test robot <lkp(a)intel.com>
Reviewed-by: Nathan Chancellor <nathan(a)kernel.org>
Signed-off-by: Linus Walleij <linus.walleij(a)linaro.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel(a)armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal(a)kernel.org>
---
arch/arm/mm/proc-v7.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S
index 48e0ef6f0dccf..aee85fd261f5d 100644
--- a/arch/arm/mm/proc-v7.S
+++ b/arch/arm/mm/proc-v7.S
@@ -91,7 +91,7 @@ ENTRY(cpu_v7_dcache_clean_area)
ret lr
ENDPROC(cpu_v7_dcache_clean_area)
-#ifdef CONFIG_ARM_PSCI
+#if defined(CONFIG_ARM_PSCI) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
.arch_extension sec
ENTRY(cpu_v7_smc_switch_mm)
stmfd sp!, {r0 - r3}
--
2.43.0