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75 lines
2.7 KiB
Diff
75 lines
2.7 KiB
Diff
From 03dab869b7b239c4e013ec82aea22e181e441cfc Mon Sep 17 00:00:00 2001
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From: David Howells <dhowells@redhat.com>
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Date: Wed, 26 Oct 2016 15:01:54 +0100
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Subject: KEYS: Fix short sprintf buffer in /proc/keys show function
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This fixes CVE-2016-7042.
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Fix a short sprintf buffer in proc_keys_show(). If the gcc stack protector
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is turned on, this can cause a panic due to stack corruption.
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The problem is that xbuf[] is not big enough to hold a 64-bit timeout
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rendered as weeks:
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(gdb) p 0xffffffffffffffffULL/(60*60*24*7)
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$2 = 30500568904943
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That's 14 chars plus NUL, not 11 chars plus NUL.
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Expand the buffer to 16 chars.
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I think the unpatched code apparently works if the stack-protector is not
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enabled because on a 32-bit machine the buffer won't be overflowed and on a
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64-bit machine there's a 64-bit aligned pointer at one side and an int that
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isn't checked again on the other side.
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The panic incurred looks something like:
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Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffff81352ebe
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CPU: 0 PID: 1692 Comm: reproducer Not tainted 4.7.2-201.fc24.x86_64 #1
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Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
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0000000000000086 00000000fbbd2679 ffff8800a044bc00 ffffffff813d941f
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ffffffff81a28d58 ffff8800a044bc98 ffff8800a044bc88 ffffffff811b2cb6
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ffff880000000010 ffff8800a044bc98 ffff8800a044bc30 00000000fbbd2679
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Call Trace:
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[<ffffffff813d941f>] dump_stack+0x63/0x84
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[<ffffffff811b2cb6>] panic+0xde/0x22a
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[<ffffffff81352ebe>] ? proc_keys_show+0x3ce/0x3d0
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[<ffffffff8109f7f9>] __stack_chk_fail+0x19/0x30
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[<ffffffff81352ebe>] proc_keys_show+0x3ce/0x3d0
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[<ffffffff81350410>] ? key_validate+0x50/0x50
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[<ffffffff8134db30>] ? key_default_cmp+0x20/0x20
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[<ffffffff8126b31c>] seq_read+0x2cc/0x390
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[<ffffffff812b6b12>] proc_reg_read+0x42/0x70
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[<ffffffff81244fc7>] __vfs_read+0x37/0x150
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[<ffffffff81357020>] ? security_file_permission+0xa0/0xc0
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[<ffffffff81246156>] vfs_read+0x96/0x130
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[<ffffffff81247635>] SyS_read+0x55/0xc0
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[<ffffffff817eb872>] entry_SYSCALL_64_fastpath+0x1a/0xa4
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Reported-by: Ondrej Kozina <okozina@redhat.com>
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Signed-off-by: David Howells <dhowells@redhat.com>
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Tested-by: Ondrej Kozina <okozina@redhat.com>
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cc: stable@vger.kernel.org
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Signed-off-by: James Morris <james.l.morris@oracle.com>
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---
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security/keys/proc.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/security/keys/proc.c b/security/keys/proc.c
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index f0611a6..b9f531c 100644
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--- a/security/keys/proc.c
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+++ b/security/keys/proc.c
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@@ -181,7 +181,7 @@ static int proc_keys_show(struct seq_file *m, void *v)
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struct timespec now;
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unsigned long timo;
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key_ref_t key_ref, skey_ref;
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- char xbuf[12];
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+ char xbuf[16];
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int rc;
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struct keyring_search_context ctx = {
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--
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cgit v1.1
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