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| author | David Howells <dhowells@redhat.com> | 2016-10-26 16:01:54 +0200 |
|---|---|---|
| committer | James Morris <james.l.morris@oracle.com> | 2016-10-27 07:03:24 +0200 |
| commit | 03dab869b7b239c4e013ec82aea22e181e441cfc (patch) | |
| tree | f4ea0ce7461ba382a66218661f8d763c04e9ef1c | |
| parent | Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert... (diff) | |
| download | linux-03dab869b7b239c4e013ec82aea22e181e441cfc.tar.xz linux-03dab869b7b239c4e013ec82aea22e181e441cfc.zip | |
KEYS: Fix short sprintf buffer in /proc/keys show function
This fixes CVE-2016-7042.
Fix a short sprintf buffer in proc_keys_show(). If the gcc stack protector
is turned on, this can cause a panic due to stack corruption.
The problem is that xbuf[] is not big enough to hold a 64-bit timeout
rendered as weeks:
(gdb) p 0xffffffffffffffffULL/(60*60*24*7)
$2 = 30500568904943
That's 14 chars plus NUL, not 11 chars plus NUL.
Expand the buffer to 16 chars.
I think the unpatched code apparently works if the stack-protector is not
enabled because on a 32-bit machine the buffer won't be overflowed and on a
64-bit machine there's a 64-bit aligned pointer at one side and an int that
isn't checked again on the other side.
The panic incurred looks something like:
Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff81352ebe
CPU: 0 PID: 1692 Comm: reproducer Not tainted 4.7.2-201.fc24.x86_64 #1
Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
0000000000000086 00000000fbbd2679 ffff8800a044bc00 ffffffff813d941f
ffffffff81a28d58 ffff8800a044bc98 ffff8800a044bc88 ffffffff811b2cb6
ffff880000000010 ffff8800a044bc98 ffff8800a044bc30 00000000fbbd2679
Call Trace:
[<ffffffff813d941f>] dump_stack+0x63/0x84
[<ffffffff811b2cb6>] panic+0xde/0x22a
[<ffffffff81352ebe>] ? proc_keys_show+0x3ce/0x3d0
[<ffffffff8109f7f9>] __stack_chk_fail+0x19/0x30
[<ffffffff81352ebe>] proc_keys_show+0x3ce/0x3d0
[<ffffffff81350410>] ? key_validate+0x50/0x50
[<ffffffff8134db30>] ? key_default_cmp+0x20/0x20
[<ffffffff8126b31c>] seq_read+0x2cc/0x390
[<ffffffff812b6b12>] proc_reg_read+0x42/0x70
[<ffffffff81244fc7>] __vfs_read+0x37/0x150
[<ffffffff81357020>] ? security_file_permission+0xa0/0xc0
[<ffffffff81246156>] vfs_read+0x96/0x130
[<ffffffff81247635>] SyS_read+0x55/0xc0
[<ffffffff817eb872>] entry_SYSCALL_64_fastpath+0x1a/0xa4
Reported-by: Ondrej Kozina <okozina@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Ondrej Kozina <okozina@redhat.com>
cc: stable@vger.kernel.org
Signed-off-by: James Morris <james.l.morris@oracle.com>
| -rw-r--r-- | security/keys/proc.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/security/keys/proc.c b/security/keys/proc.c index f0611a6368cd..b9f531c9e4fa 100644 --- a/security/keys/proc.c +++ b/security/keys/proc.c @@ -181,7 +181,7 @@ static int proc_keys_show(struct seq_file *m, void *v) struct timespec now; unsigned long timo; key_ref_t key_ref, skey_ref; - char xbuf[12]; + char xbuf[16]; int rc; struct keyring_search_context ctx = { |