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Date: Sat, 28 Nov 2015 09:10:19 -0800
From: Eric Dumazet <eric.dumazet@...il.com>
To: Sasha Levin <sasha.levin@...cle.com>,
Vlad Yasevich <vyasevich@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
syzkaller <syzkaller@...glegroups.com>
Subject: Re: net: use after free in ip6_make_skb
On Sat, 2015-11-28 at 11:33 -0500, Sasha Levin wrote:
> Hi,
>
> Fuzzing with syzkaller on the latest -next kernel produced this error:
>
> [ 891.389013] ==================================================================
>
> [ 891.390006] BUG: KASAN: use-after-free in ip6_make_skb+0x106/0x3d0 at addr ffff8806e9773a34
>
> [ 891.393459] Read of size 2 by task syzkaller_execu/8350
>
> [ 891.394128] =============================================================================
>
> [ 891.395121] BUG kmalloc-64 (Not tainted): kasan: bad access detected
>
> [ 891.395886] -----------------------------------------------------------------------------
>
> [ 891.395886]
>
> [ 891.398479] Disabling lock debugging due to kernel taint
>
> [ 891.399156] INFO: Allocated in p9pdu_vreadf+0x7d4/0x1da0 age=2 cpu=12 pid=8331
>
> [ 891.400255] ___slab_alloc+0x434/0x5b0
>
> [ 891.400917] __slab_alloc.isra.37+0x79/0xd0
>
> [ 891.401642] __kmalloc+0x12f/0x390
>
> [ 891.402172] pipe_fcntl+0x195/0x4c0
>
> [ 891.402743] SyS_fcntl+0xd70/0xe50
>
> [ 891.403162] entry_SYSCALL_64_fastpath+0x35/0x9e
>
> [ 891.403715] INFO: Freed in kfree_put_link+0x1a/0x20 age=6 cpu=12 pid=8331
>
> [ 891.404349] __slab_free+0x5c/0x2b0
>
> [ 891.404665] kfree+0x281/0x2f0
>
> [ 891.404915] kfree_put_link+0x1a/0x20
>
> [ 891.405201] path_openat+0x391f/0x5040
>
> [ 891.405508] do_filp_open+0x1b8/0x250
>
> [ 891.405814] do_open_execat+0x105/0x4d0
>
> [ 891.406295] open_exec+0x3b/0x60
>
> [ 891.406802] INFO: Slab 0xffffea001ba5dc00 objects=41 used=20 fp=0xffff8806e9773a30 flags=0x2fffff80004080
>
> [ 891.407978] INFO: Object 0xffff8806e9773a30 @offset=14896 fp=0xffff8806e9772028
>
> [ 891.407978]
>
> [ 891.408888] Bytes b4 ffff8806e9773a20: e3 07 05 00 01 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a ........ZZZZZZZZ
>
> [ 891.410121] Object ffff8806e9773a30: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
>
> [ 891.411425] Object ffff8806e9773a40: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
>
> [ 891.412603] Object ffff8806e9773a50: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
>
> [ 891.413775] Object ffff8806e9773a60: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5 kkkkkkkkkkkkkkk.
>
> [ 891.414977] Redzone ffff8806e9773a70: bb bb bb bb bb bb bb bb ........
>
> [ 891.416092] Padding ffff8806e9773bb0: 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZ
>
> [ 891.417221] CPU: 7 PID: 8350 Comm: syzkaller_execu Tainted: G B 4.4.0-rc2-next-20151126-sasha-00007-g7083bec-dirty #2655
>
> [ 891.424771] Call Trace:
>
> [ 891.425454] dump_stack (lib/dump_stack.c:52)
> [ 891.426433] print_trailer (mm/slub.c:655)
> [ 891.427482] object_err (mm/slub.c:662)
> [ 891.428495] kasan_report_error (mm/kasan/report.c:138 mm/kasan/report.c:236)
> [ 891.430825] __asan_report_load2_noabort (mm/kasan/report.c:278)
> [ 891.432908] ip6_make_skb (net/ipv6/ip6_output.c:1757)
> [ 891.446294] udpv6_sendmsg (include/linux/err.h:40 net/ipv6/udp.c:1319)
> [ 891.461731] inet_sendmsg (net/ipv4/af_inet.c:733)
> [ 891.465359] sock_sendmsg (net/socket.c:611 net/socket.c:620)
> [ 891.466211] sock_write_iter (net/socket.c:820)
> [ 891.470869] __vfs_write (fs/read_write.c:480 fs/read_write.c:492)
> [ 891.473525] vfs_write (fs/read_write.c:540)
> [ 891.474341] SyS_write (fs/read_write.c:587 fs/read_write.c:578)
> [ 891.477995] entry_SYSCALL_64_fastpath (arch/x86/entry/entry_64.S:188)
> [ 891.478975] Memory state around the buggy address:
>
> [ 891.479722] ffff8806e9773900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>
> [ 891.480830] ffff8806e9773980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>
> [ 891.481954] >ffff8806e9773a00: fc fc fc fc fc fc 00 00 00 00 00 00 00 fc fc fc
>
> [ 891.483025] ^
>
> [ 891.483622] ffff8806e9773a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>
> [ 891.484469] ffff8806e9773b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>
> [ 891.485307] ==================================================================
>
>
> Thanks,
> Sasha
Very similar to a report sent earlier by Dmitry.
Bug probably added by :
commit 03485f2adcde0c2d4e9228b659be78e872486bbb
Author: Vlad Yasevich <vyasevich@...il.com>
Date: Sat Jan 31 10:40:17 2015 -0500
udpv6: Add lockless sendmsg() support
This commit adds the same functionaliy to IPv6 that
commit 903ab86d195cca295379699299c5fc10beba31c7
Author: Herbert Xu <herbert@...dor.apana.org.au>
Date: Tue Mar 1 02:36:48 2011 +0000
udp: Add lockless transmit path
added to IPv4.
UDP transmit path can now run without a socket lock,
thus allowing multiple threads to send to a single socket
more efficiently.
This is only used when corking/MSG_MORE is not used.
Signed-off-by: Vladislav Yasevich <vyasevic@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
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