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authorAndrey Ryabinin <a.ryabinin@samsung.com>2014-11-08 17:48:05 +0300
committerCasey Schaufler <casey@schaufler-ca.com>2014-11-21 13:14:22 -0800
commit5c1b66240b7f4abc29c618a768121d6a00f4c95a (patch)
treea0d1ba1ee1e15a3460eca924c06371aec5e234b7 /security/smack/smack_access.c
parent1a5b472bde752783e0a31b59c61c9ff5b37a0983 (diff)
downloadlinux-5c1b66240b7f4abc29c618a768121d6a00f4c95a.tar.gz
security: smack: fix out-of-bounds access in smk_parse_smack()
Setting smack label on file (e.g. 'attr -S -s SMACK64 -V "test" test') triggered following spew on the kernel with KASan applied: ================================================================== BUG: AddressSanitizer: out of bounds access in strncpy+0x28/0x60 at addr ffff8800059ad064 ============================================================================= BUG kmalloc-8 (Not tainted): kasan error ----------------------------------------------------------------------------- Disabling lock debugging due to kernel taint INFO: Slab 0xffffea0000166b40 objects=128 used=7 fp=0xffff8800059ad080 flags=0x4000000000000080 INFO: Object 0xffff8800059ad060 @offset=96 fp=0xffff8800059ad080 Bytes b4 ffff8800059ad050: a0 df 9a 05 00 88 ff ff 5a 5a 5a 5a 5a 5a 5a 5a ........ZZZZZZZZ Object ffff8800059ad060: 74 65 73 74 6b 6b 6b a5 testkkk. Redzone ffff8800059ad068: cc cc cc cc cc cc cc cc ........ Padding ffff8800059ad078: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ CPU: 0 PID: 528 Comm: attr Tainted: G B 3.18.0-rc1-mm1+ #5 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 0000000000000000 ffff8800059ad064 ffffffff81534cf2 ffff880005a5bc40 ffffffff8112fe1a 0000000100800006 0000000f059ad060 ffff880006000f90 0000000000000296 ffffea0000166b40 ffffffff8107ca97 ffff880005891060 Call Trace: ? dump_stack (lib/dump_stack.c:52) ? kasan_report_error (mm/kasan/report.c:102 mm/kasan/report.c:178) ? preempt_count_sub (kernel/sched/core.c:2651) ? __asan_load1 (mm/kasan/kasan.h:50 mm/kasan/kasan.c:248 mm/kasan/kasan.c:358) ? strncpy (lib/string.c:121) ? strncpy (lib/string.c:121) ? smk_parse_smack (security/smack/smack_access.c:457) ? setxattr (fs/xattr.c:343) ? smk_import_entry (security/smack/smack_access.c:514) ? smack_inode_setxattr (security/smack/smack_lsm.c:1093 (discriminator 1)) ? security_inode_setxattr (security/security.c:602) ? vfs_setxattr (fs/xattr.c:134) ? setxattr (fs/xattr.c:343) ? setxattr (fs/xattr.c:360) ? get_parent_ip (kernel/sched/core.c:2606) ? preempt_count_sub (kernel/sched/core.c:2651) ? __percpu_counter_add (arch/x86/include/asm/preempt.h:98 lib/percpu_counter.c:90) ? get_parent_ip (kernel/sched/core.c:2606) ? preempt_count_sub (kernel/sched/core.c:2651) ? __mnt_want_write (arch/x86/include/asm/preempt.h:98 fs/namespace.c:359) ? path_setxattr (fs/xattr.c:380) ? SyS_lsetxattr (fs/xattr.c:397) ? system_call_fastpath (arch/x86/kernel/entry_64.S:423) Read of size 1 by task attr: Memory state around the buggy address: ffff8800059ace80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff8800059acf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff8800059acf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff8800059ad000: 00 fc fc fc 00 fc fc fc 05 fc fc fc 04 fc fc fc ^ ffff8800059ad080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8800059ad100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8800059ad180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== strncpy() copies one byte more than the source string has. Fix this by passing the correct length to strncpy(). Now we can remove initialization of the last byte in 'smack' string because kzalloc() already did this for us. Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Diffstat (limited to 'security/smack/smack_access.c')
-rw-r--r--security/smack/smack_access.c7
1 files changed, 3 insertions, 4 deletions
diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index 999224fe8593..1158430f5bb9 100644
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -452,10 +452,9 @@ char *smk_parse_smack(const char *string, int len)
return NULL;
smack = kzalloc(i + 1, GFP_KERNEL);
- if (smack != NULL) {
- strncpy(smack, string, i + 1);
- smack[i] = '\0';
- }
+ if (smack != NULL)
+ strncpy(smack, string, i);
+
return smack;
}