[syzbot] [crypto?] WARNING in extract_iter_to_sg

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3674fbf0451d Merge git://git.kernel.org/pub/scm/linux/kern..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=10e4a802a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=c9bf1936936ca698
dashboard link: https://syzkaller.appspot.com/bug?extid=f2c120b449b209d89efa
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/42ed556782c3/disk-3674fbf0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1913e16e8565/vmlinux-3674fbf0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/469804b58a7c/bzImage-3674fbf0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f2c120...@syzkaller.appspotmail.com

extract_iter_to_sg(3) unsupported
------------[ cut here ]------------
WARNING: CPU: 0 PID: 26699 at lib/scatterlist.c:1362 extract_iter_to_sg lib/scatterlist.c:1361 [inline]
WARNING: CPU: 0 PID: 26699 at lib/scatterlist.c:1362 extract_iter_to_sg+0xf02/0x1960 lib/scatterlist.c:1339
Modules linked in:
CPU: 0 PID: 26699 Comm: syz-executor.2 Not tainted 6.4.0-rc7-syzkaller-01944-g3674fbf0451d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
RIP: 0010:extract_iter_to_sg lib/scatterlist.c:1362 [inline]
RIP: 0010:extract_iter_to_sg+0xf02/0x1960 lib/scatterlist.c:1339
Code: ff ff 48 c1 e3 06 48 01 c3 e9 8c fe ff ff e8 65 78 73 fd 40 0f b6 d5 48 c7 c6 e0 c7 a6 8a 48 c7 c7 00 c7 a6 8a e8 ee 58 57 fd <0f> 0b 48 c7 44 24 18 fb ff ff ff e9 1b fc ff ff e8 39 78 73 fd 48
RSP: 0018:ffffc90009937680 EFLAGS: 00010286
RAX: 0000000000000021 RBX: 0000000000000001 RCX: ffffc9000c714000
RDX: 0000000000000000 RSI: ffffffff8168bc0c RDI: 0000000000000005
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 0000000000000001 R12: ffff88802dcea248
R13: ffff88802dcea268 R14: ffff88802dcea268 R15: ffffc90009937a40
FS: 00007fc151532700(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc14effe718 CR3: 000000002b366000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
af_alg_get_rsgl+0x24d/0x7c0 crypto/af_alg.c:1249
_skcipher_recvmsg crypto/algif_skcipher.c:77 [inline]
skcipher_recvmsg+0x8ee/0xe40 crypto/algif_skcipher.c:157
sock_recvmsg_nosec net/socket.c:1019 [inline]
sock_recvmsg+0xe2/0x160 net/socket.c:1040
sock_read_iter+0x2bd/0x3b0 net/socket.c:1106
call_read_iter include/linux/fs.h:1862 [inline]
generic_file_splice_read+0x182/0x4b0 fs/splice.c:420
sock_splice_read+0xed/0x120 net/socket.c:1076
do_splice_to+0x1b9/0x240 fs/splice.c:1007
splice_file_to_pipe+0x104/0x120 fs/splice.c:1246
do_splice+0x10e7/0x1e50 fs/splice.c:1335
__do_splice+0x14e/0x270 fs/splice.c:1385
__do_sys_splice fs/splice.c:1596 [inline]
__se_sys_splice fs/splice.c:1578 [inline]
__x64_sys_splice+0x19c/0x250 fs/splice.c:1578
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fc15088c389
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc151532168 EFLAGS: 00000246 ORIG_RAX: 0000000000000113
RAX: ffffffffffffffda RBX: 00007fc1509ac120 RCX: 00007fc15088c389
RDX: 000000000000000f RSI: 0000000000000000 RDI: 0000000000000006
RBP: 00007fc1508d7493 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fffc693848f R14: 00007fc151532300 R15: 0000000000022000
</TASK>


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[Herbert Xu]

On Wed, Jul 05, 2023 at 11:02:16AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 3674fbf0451d Merge git://git.kernel.org/pub/scm/linux/kern..
> git tree: net
> console output: https://syzkaller.appspot.com/x/log.txt?x=10e4a802a80000
> kernel config: https://syzkaller.appspot.com/x/.config?x=c9bf1936936ca698
> dashboard link: https://syzkaller.appspot.com/bug?extid=f2c120b449b209d89efa
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>
> Unfortunately, I don't have any reproducer for this issue yet.

Hi David:

This looks like another regression. It's not clear whether this
one will be fixed by your latest patch. Could you please take a
look?

Thanks,
--
Email: Herbert Xu <her...@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

[David Howells]

> CPU: 0 PID: 26699 Comm: syz-executor.2 Not tainted 6.4.0-rc7-syzkaller-01944-g3674fbf0451d #0

Looking at the version string, this is from net-next before the merger with
Linus's tree after the point where Linus had merged:

https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git/log/?h=for-6.5/splice

> extract_iter_to_sg(3) unsupported

This is ITER_PIPE (type 3) before is removed by:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3fc40265ae2b48a7475c41c5c0b256374c419f4b

From that point on ITER_XARRAY is type 3 and there's a case for that in
extract_iter_to_sg().

So the fix for this is to merge it with the splice tree - which Linus has
already done, so this should be fixed upstream.

With hindsight, I should've used iov_iter_get_pages*() rather than
iov_iter_extract_pages() and extract_iter_to_sg() in the networking code
recvmsg() path until after the merge.

David

[David Howells]

#syz fix: iov_iter: Kill ITER_PIPE