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| author | Will Deacon <will.deacon@arm.com> | 2019-04-05 18:39:38 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-04-05 16:02:31 -1000 |
| commit | 9002b21465fa4d829edfc94a5a441005cffaa972 (patch) | |
| tree | 7f749f602dbe3a8e9b72a334851ea5a85fa6fc8b /kernel/sysctl.c | |
| parent | e91455217d8c7b128c158432869f6e697283f3ec (diff) | |
| download | lwn-9002b21465fa4d829edfc94a5a441005cffaa972.tar.gz lwn-9002b21465fa4d829edfc94a5a441005cffaa972.zip | |
kernel/sysctl.c: fix out-of-bounds access when setting file-max
Commit 32a5ad9c2285 ("sysctl: handle overflow for file-max") hooked up
min/max values for the file-max sysctl parameter via the .extra1 and
.extra2 fields in the corresponding struct ctl_table entry.
Unfortunately, the minimum value points at the global 'zero' variable,
which is an int. This results in a KASAN splat when accessed as a long
by proc_doulongvec_minmax on 64-bit architectures:
| BUG: KASAN: global-out-of-bounds in __do_proc_doulongvec_minmax+0x5d8/0x6a0
| Read of size 8 at addr ffff2000133d1c20 by task systemd/1
|
| CPU: 0 PID: 1 Comm: systemd Not tainted 5.1.0-rc3-00012-g40b114779944 #2
| Hardware name: linux,dummy-virt (DT)
| Call trace:
| dump_backtrace+0x0/0x228
| show_stack+0x14/0x20
| dump_stack+0xe8/0x124
| print_address_description+0x60/0x258
| kasan_report+0x140/0x1a0
| __asan_report_load8_noabort+0x18/0x20
| __do_proc_doulongvec_minmax+0x5d8/0x6a0
| proc_doulongvec_minmax+0x4c/0x78
| proc_sys_call_handler.isra.19+0x144/0x1d8
| proc_sys_write+0x34/0x58
| __vfs_write+0x54/0xe8
| vfs_write+0x124/0x3c0
| ksys_write+0xbc/0x168
| __arm64_sys_write+0x68/0x98
| el0_svc_common+0x100/0x258
| el0_svc_handler+0x48/0xc0
| el0_svc+0x8/0xc
|
| The buggy address belongs to the variable:
| zero+0x0/0x40
|
| Memory state around the buggy address:
| ffff2000133d1b00: 00 00 00 00 00 00 00 00 fa fa fa fa 04 fa fa fa
| ffff2000133d1b80: fa fa fa fa 04 fa fa fa fa fa fa fa 04 fa fa fa
| >ffff2000133d1c00: fa fa fa fa 04 fa fa fa fa fa fa fa 00 00 00 00
| ^
| ffff2000133d1c80: fa fa fa fa 00 fa fa fa fa fa fa fa 00 00 00 00
| ffff2000133d1d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
Fix the splat by introducing a unsigned long 'zero_ul' and using that
instead.
Link: http://lkml.kernel.org/r/20190403153409.17307-1-will.deacon@arm.com
Fixes: 32a5ad9c2285 ("sysctl: handle overflow for file-max")
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Christian Brauner <christian@brauner.io>
Cc: Kees Cook <keescook@chromium.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sysctl.c')
| -rw-r--r-- | kernel/sysctl.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/sysctl.c b/kernel/sysctl.c index e5da394d1ca3..c9ec050bcf46 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -128,6 +128,7 @@ static int zero; static int __maybe_unused one = 1; static int __maybe_unused two = 2; static int __maybe_unused four = 4; +static unsigned long zero_ul; static unsigned long one_ul = 1; static unsigned long long_max = LONG_MAX; static int one_hundred = 100; @@ -1750,7 +1751,7 @@ static struct ctl_table fs_table[] = { .maxlen = sizeof(files_stat.max_files), .mode = 0644, .proc_handler = proc_doulongvec_minmax, - .extra1 = &zero, + .extra1 = &zero_ul, .extra2 = &long_max, }, { |