From: Matteo Croce mcroce@microsoft.com
The parsing of the reboot= cmdline has two major errors: - a missing bound check can crash the system on reboot - parsing of the cpu number only works if specified last
Fix both, along with a small code refactor.
v1->v2: As Petr suggested, don't force base 10 in simple_strtoul(), so hex values are accepted as well.
Matteo Croce (2): reboot: fix overflow parsing reboot cpu number reboot: fix parsing of reboot cpu number
kernel/reboot.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-)
From: Matteo Croce mcroce@microsoft.com
Limit the CPU number to num_possible_cpus(), because setting it to a value lower than INT_MAX but higher than NR_CPUS produces the following error on reboot and shutdown:
BUG: unable to handle page fault for address: ffffffff90ab1bb0 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 1c09067 P4D 1c09067 PUD 1c0a063 PMD 0 Oops: 0000 [#1] SMP CPU: 1 PID: 1 Comm: systemd-shutdow Not tainted 5.9.0-rc8-kvm #110 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 RIP: 0010:migrate_to_reboot_cpu+0xe/0x60 Code: ea ea 00 48 89 fa 48 c7 c7 30 57 f1 81 e9 fa ef ff ff 66 2e 0f 1f 84 00 00 00 00 00 53 8b 1d d5 ea ea 00 e8 14 33 fe ff 89 da <48> 0f a3 15 ea fc bd 00 48 89 d0 73 29 89 c2 c1 e8 06 65 48 8b 3c RSP: 0018:ffffc90000013e08 EFLAGS: 00010246 RAX: ffff88801f0a0000 RBX: 0000000077359400 RCX: 0000000000000000 RDX: 0000000077359400 RSI: 0000000000000002 RDI: ffffffff81c199e0 RBP: ffffffff81c1e3c0 R08: ffff88801f41f000 R09: ffffffff81c1e348 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 00007f32bedf8830 R14: 00000000fee1dead R15: 0000000000000000 FS: 00007f32bedf8980(0000) GS:ffff88801f480000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffff90ab1bb0 CR3: 000000001d057000 CR4: 00000000000006a0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __do_sys_reboot.cold+0x34/0x5b ? vfs_writev+0x92/0xc0 ? do_writev+0x52/0xd0 do_syscall_64+0x2d/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f32bfaaecd3 Code: 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 89 fa be 69 19 12 28 bf ad de e1 fe b8 a9 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 8b 15 89 81 0c 00 f7 d8 RSP: 002b:00007fff6265fb58 EFLAGS: 00000202 ORIG_RAX: 00000000000000a9 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f32bfaaecd3 RDX: 0000000001234567 RSI: 0000000028121969 RDI: 00000000fee1dead RBP: 0000000000000000 R08: 0000000000008020 R09: 00007fff6265ef60 R10: 00007f32bedf8830 R11: 0000000000000202 R12: 0000000000000000 R13: 0000557bba2c51c0 R14: 0000000000000000 R15: 00007fff6265fbc8 CR2: ffffffff90ab1bb0 ---[ end trace b813e80157136563 ]--- RIP: 0010:migrate_to_reboot_cpu+0xe/0x60 Code: ea ea 00 48 89 fa 48 c7 c7 30 57 f1 81 e9 fa ef ff ff 66 2e 0f 1f 84 00 00 00 00 00 53 8b 1d d5 ea ea 00 e8 14 33 fe ff 89 da <48> 0f a3 15 ea fc bd 00 48 89 d0 73 29 89 c2 c1 e8 06 65 48 8b 3c RSP: 0018:ffffc90000013e08 EFLAGS: 00010246 RAX: ffff88801f0a0000 RBX: 0000000077359400 RCX: 0000000000000000 RDX: 0000000077359400 RSI: 0000000000000002 RDI: ffffffff81c199e0 RBP: ffffffff81c1e3c0 R08: ffff88801f41f000 R09: ffffffff81c1e348 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 00007f32bedf8830 R14: 00000000fee1dead R15: 0000000000000000 FS: 00007f32bedf8980(0000) GS:ffff88801f480000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffff90ab1bb0 CR3: 000000001d057000 CR4: 00000000000006a0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 Kernel Offset: disabled ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 ]---
Fixes: 1b3a5d02ee07 ("reboot: move arch/x86 reboot= handling to generic kernel") Signed-off-by: Matteo Croce mcroce@microsoft.com --- kernel/reboot.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/kernel/reboot.c b/kernel/reboot.c index e7b78d5ae1ab..c4e7965c39b9 100644 --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -558,11 +558,19 @@ static int __init reboot_setup(char *str) rc = kstrtoint(str+1, 0, &reboot_cpu); if (rc) return rc; + if (reboot_cpu >= num_possible_cpus()) { + reboot_cpu = 0; + return -ERANGE; + } } else if (str[1] == 'm' && str[2] == 'p' && isdigit(*(str+3))) { rc = kstrtoint(str+3, 0, &reboot_cpu); if (rc) return rc; + if (reboot_cpu >= num_possible_cpus()) { + reboot_cpu = 0; + return -ERANGE; + } } else *mode = REBOOT_SOFT; break;
On Tue, Oct 27, 2020 at 02:35:44PM +0100, Matteo Croce wrote:
From: Matteo Croce mcroce@microsoft.com
Limit the CPU number to num_possible_cpus(), because setting it to a value lower than INT_MAX but higher than NR_CPUS produces the following error on reboot and shutdown:
BUG: unable to handle page fault for address: ffffffff90ab1bb0 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 1c09067 P4D 1c09067 PUD 1c0a063 PMD 0 Oops: 0000 [#1] SMP CPU: 1 PID: 1 Comm: systemd-shutdow Not tainted 5.9.0-rc8-kvm #110 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014 RIP: 0010:migrate_to_reboot_cpu+0xe/0x60 Code: ea ea 00 48 89 fa 48 c7 c7 30 57 f1 81 e9 fa ef ff ff 66 2e 0f 1f 84 00 00 00 00 00 53 8b 1d d5 ea ea 00 e8 14 33 fe ff 89 da <48> 0f a3 15 ea fc bd 00 48 89 d0 73 29 89 c2 c1 e8 06 65 48 8b 3c RSP: 0018:ffffc90000013e08 EFLAGS: 00010246 RAX: ffff88801f0a0000 RBX: 0000000077359400 RCX: 0000000000000000 RDX: 0000000077359400 RSI: 0000000000000002 RDI: ffffffff81c199e0 RBP: ffffffff81c1e3c0 R08: ffff88801f41f000 R09: ffffffff81c1e348 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 00007f32bedf8830 R14: 00000000fee1dead R15: 0000000000000000 FS: 00007f32bedf8980(0000) GS:ffff88801f480000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffff90ab1bb0 CR3: 000000001d057000 CR4: 00000000000006a0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __do_sys_reboot.cold+0x34/0x5b ? vfs_writev+0x92/0xc0 ? do_writev+0x52/0xd0 do_syscall_64+0x2d/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7f32bfaaecd3 Code: 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 89 fa be 69 19 12 28 bf ad de e1 fe b8 a9 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 8b 15 89 81 0c 00 f7 d8 RSP: 002b:00007fff6265fb58 EFLAGS: 00000202 ORIG_RAX: 00000000000000a9 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f32bfaaecd3 RDX: 0000000001234567 RSI: 0000000028121969 RDI: 00000000fee1dead RBP: 0000000000000000 R08: 0000000000008020 R09: 00007fff6265ef60 R10: 00007f32bedf8830 R11: 0000000000000202 R12: 0000000000000000 R13: 0000557bba2c51c0 R14: 0000000000000000 R15: 00007fff6265fbc8 CR2: ffffffff90ab1bb0 ---[ end trace b813e80157136563 ]--- RIP: 0010:migrate_to_reboot_cpu+0xe/0x60 Code: ea ea 00 48 89 fa 48 c7 c7 30 57 f1 81 e9 fa ef ff ff 66 2e 0f 1f 84 00 00 00 00 00 53 8b 1d d5 ea ea 00 e8 14 33 fe ff 89 da <48> 0f a3 15 ea fc bd 00 48 89 d0 73 29 89 c2 c1 e8 06 65 48 8b 3c RSP: 0018:ffffc90000013e08 EFLAGS: 00010246 RAX: ffff88801f0a0000 RBX: 0000000077359400 RCX: 0000000000000000 RDX: 0000000077359400 RSI: 0000000000000002 RDI: ffffffff81c199e0 RBP: ffffffff81c1e3c0 R08: ffff88801f41f000 R09: ffffffff81c1e348 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 00007f32bedf8830 R14: 00000000fee1dead R15: 0000000000000000 FS: 00007f32bedf8980(0000) GS:ffff88801f480000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffff90ab1bb0 CR3: 000000001d057000 CR4: 00000000000006a0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 Kernel Offset: disabled ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000009 ]---Fixes: 1b3a5d02ee07 ("reboot: move arch/x86 reboot= handling to generic kernel") Signed-off-by: Matteo Croce mcroce@microsoft.com
kernel/reboot.c | 8 ++++++++ 1 file changed, 8 insertions(+)
<formletter>
This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.
</formletter>
On Tue 2020-10-27 14:42:43, Greg KH wrote:
On Tue, Oct 27, 2020 at 02:35:44PM +0100, Matteo Croce wrote:
From: Matteo Croce mcroce@microsoft.com
Limit the CPU number to num_possible_cpus(), because setting it to a value lower than INT_MAX but higher than NR_CPUS produces the following error on reboot and shutdown:
Fixes: 1b3a5d02ee07 ("reboot: move arch/x86 reboot= handling to generic kernel") Signed-off-by: Matteo Croce mcroce@microsoft.com
Reviewed-by: Petr Mladek pmladek@suse.com
<formletter>
This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.
</formletter>
The best way is to add the following line before Signed-off-by line:
Cc: stable@vger.kernel.org
Best Regards, Petr
From: Matteo Croce mcroce@microsoft.com
The kernel cmdline reboot= argument allows to specify the CPU used for rebooting, with the syntax `s####` among the other flags, e.g.
reboot=soft,s4 reboot=warm,s31,force
In the early days the parsing was done with simple_strtoul(), later deprecated in favor of the safer kstrtoint() which handles overflow.
But kstrtoint() returns -EINVAL if there are non-digit characters in a string, so if this flag is not the last given, it's silently ignored as well as the subsequent ones.
To fix it, revert the usage of simple_strtoul(), which is no longer deprecated, and restore the old behaviour.
While at it, merge two identical code blocks into one.
Fixes: 616feab75397 ("kernel/reboot.c: convert simple_strtoul to kstrtoint") Signed-off-by: Matteo Croce mcroce@microsoft.com --- kernel/reboot.c | 30 ++++++++++++------------------ 1 file changed, 12 insertions(+), 18 deletions(-)
diff --git a/kernel/reboot.c b/kernel/reboot.c index c4e7965c39b9..a09c5937c0b6 100644 --- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -552,25 +552,19 @@ static int __init reboot_setup(char *str)
case 's': { - int rc; - - if (isdigit(*(str+1))) { - rc = kstrtoint(str+1, 0, &reboot_cpu); - if (rc) - return rc; - if (reboot_cpu >= num_possible_cpus()) { - reboot_cpu = 0; - return -ERANGE; - } - } else if (str[1] == 'm' && str[2] == 'p' && - isdigit(*(str+3))) { - rc = kstrtoint(str+3, 0, &reboot_cpu); - if (rc) - return rc; - if (reboot_cpu >= num_possible_cpus()) { - reboot_cpu = 0; + int cpu; + + /* + * reboot_cpu is s[mp]#### with #### being the processor + * to be used for rebooting. Skip 's' or 'smp' prefix. + */ + str += str[1] == 'm' && str[2] == 'p' ? 3 : 1; + + if (isdigit(str[0])) { + cpu = simple_strtoul(str, NULL, 0); + if (cpu >= num_possible_cpus()) return -ERANGE; - } + reboot_cpu = cpu; } else *mode = REBOOT_SOFT; break;
On Tue, Oct 27, 2020 at 02:35:45PM +0100, Matteo Croce wrote:
From: Matteo Croce mcroce@microsoft.com
The kernel cmdline reboot= argument allows to specify the CPU used for rebooting, with the syntax `s####` among the other flags, e.g.
reboot=soft,s4 reboot=warm,s31,force
In the early days the parsing was done with simple_strtoul(), later deprecated in favor of the safer kstrtoint() which handles overflow.
But kstrtoint() returns -EINVAL if there are non-digit characters in a string, so if this flag is not the last given, it's silently ignored as well as the subsequent ones.
To fix it, revert the usage of simple_strtoul(), which is no longer deprecated, and restore the old behaviour.
While at it, merge two identical code blocks into one.
Fixes: 616feab75397 ("kernel/reboot.c: convert simple_strtoul to kstrtoint") Signed-off-by: Matteo Croce mcroce@microsoft.com
kernel/reboot.c | 30 ++++++++++++------------------ 1 file changed, 12 insertions(+), 18 deletions(-)
<formletter>
This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.
</formletter>
On Tue 2020-10-27 14:35:45, Matteo Croce wrote:
From: Matteo Croce mcroce@microsoft.com
The kernel cmdline reboot= argument allows to specify the CPU used for rebooting, with the syntax `s####` among the other flags, e.g.
reboot=soft,s4 reboot=warm,s31,force
In the early days the parsing was done with simple_strtoul(), later deprecated in favor of the safer kstrtoint() which handles overflow.
But kstrtoint() returns -EINVAL if there are non-digit characters in a string, so if this flag is not the last given, it's silently ignored as well as the subsequent ones.
To fix it, revert the usage of simple_strtoul(), which is no longer deprecated, and restore the old behaviour.
While at it, merge two identical code blocks into one.
--- a/kernel/reboot.c +++ b/kernel/reboot.c @@ -552,25 +552,19 @@ static int __init reboot_setup(char *str) case 's': {
int rc;if (isdigit(*(str+1))) {rc = kstrtoint(str+1, 0, &reboot_cpu);if (rc)return rc;if (reboot_cpu >= num_possible_cpus()) {reboot_cpu = 0;return -ERANGE;}} else if (str[1] == 'm' && str[2] == 'p' &&isdigit(*(str+3))) {rc = kstrtoint(str+3, 0, &reboot_cpu);if (rc)return rc;if (reboot_cpu >= num_possible_cpus()) {reboot_cpu = 0;
^^^^^^
int cpu;/** reboot_cpu is s[mp]#### with #### being the processor* to be used for rebooting. Skip 's' or 'smp' prefix.*/str += str[1] == 'm' && str[2] == 'p' ? 3 : 1;if (isdigit(str[0])) {cpu = simple_strtoul(str, NULL, 0);if (cpu >= num_possible_cpus()) return -ERANGE;
}
reboot_cpu = cpu;
The original value stays when the new one is out of range. It is small functional change that should get mentioned in the commit message or better fixed separately.
Hmm, I suggest to split this into 3 patches and switch the order:
+ 1st patch should simply revert the commit 616feab75397 ("kernel/reboot.c: convert simple_strtoul to kstrtoint").
+ 2nd patch should merge the two branches without any functional change.
+ 3rd patch should add the check for num_possible_cpus() and update the value only when it is valid.
I am sorry that I did not suggested this when reviewed v1. I have missed this functional change at that time.
Best Regards, Petr
On Tue, Oct 27, 2020 at 02:35:43PM +0100, Matteo Croce wrote:
From: Matteo Croce mcroce@microsoft.com
The parsing of the reboot= cmdline has two major errors:
- a missing bound check can crash the system on reboot
- parsing of the cpu number only works if specified last
Fix both, along with a small code refactor.
v1->v2: As Petr suggested, don't force base 10 in simple_strtoul(), so hex values are accepted as well.
Matteo Croce (2): reboot: fix overflow parsing reboot cpu number reboot: fix parsing of reboot cpu number
kernel/reboot.c | 24 +++++++++++++----------- 1 file changed, 13 insertions(+), 11 deletions(-)
-- 2.28.0
<formletter>
This is not the correct way to submit patches for inclusion in the stable kernel tree. Please read: https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html for how to do this properly.
</formletter>
linux-stable-mirror@lists.linaro.org
-
Greg KH -
Matteo Croce -
Petr Mladek