Re: [PATCH] iov-iter: do not return more bytes than requested in iov_iter_extract_bvec_pages()

[Jens Axboe <axboe@kernel.dk>]

On Fri, 01 Nov 2024 17:47:55 +0000, Eric Dumazet wrote:
> syzbot found a way to crash UDP sendpage.
> 
> Root cause is that iov_iter_extract_bvec_pages() is returning more bytes than
> requested by ip_append_data().
> 
> Oops: general protection fault, probably for non-canonical address 0xed2e87ee8f0cadc6: 0000 [#1] PREEMPT SMP KASAN PTI
> KASAN: maybe wild-memory-access in range [0x69745f7478656e30-0x69745f7478656e37]
> CPU: 1 UID: 0 PID: 5869 Comm: syz-executor171 Not tainted 6.12.0-rc5-next-20241031-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
>  RIP: 0010:_compound_head include/linux/page-flags.h:242 [inline]
>  RIP: 0010:put_page+0x23/0x260 include/linux/mm.h:1552
> Code: 90 90 90 90 90 90 90 55 41 57 41 56 53 49 89 fe 48 bd 00 00 00 00 00 fc ff df e8 d8 ae 0d f8 49 8d 5e 08 48 89 d8 48 c1 e8 03 <80> 3c 28 00 74 08 48 89 df e8 5f e5 77 f8 48 8b 1b 48 89 de 48 83
> RSP: 0018:ffffc90003f970a8 EFLAGS: 00010207
> RAX: 0d2e8bee8f0cadc6 RBX: 69745f7478656e36 RCX: ffff8880306d3c00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 69745f7478656e2e
> RBP: dffffc0000000000 R08: ffffffff898706fd R09: 1ffffffff203a076
> R10: dffffc0000000000 R11: fffffbfff203a077 R12: 0000000000000000
> R13: ffff88807fd7a842 R14: 69745f7478656e2e R15: 69745f7478656e2e
> FS:  0000555590726380(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000045ad50 CR3: 0000000025350000 CR4: 00000000003526f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>   skb_page_unref include/linux/skbuff_ref.h:43 [inline]
>   __skb_frag_unref include/linux/skbuff_ref.h:56 [inline]
>   skb_release_data+0x483/0x8a0 net/core/skbuff.c:1119
>   skb_release_all net/core/skbuff.c:1190 [inline]
>   __kfree_skb net/core/skbuff.c:1204 [inline]
>   sk_skb_reason_drop+0x1c9/0x380 net/core/skbuff.c:1242
>   kfree_skb_reason include/linux/skbuff.h:1262 [inline]
>   kfree_skb include/linux/skbuff.h:1271 [inline]
>   __ip_flush_pending_frames net/ipv4/ip_output.c:1538 [inline]
>   ip_flush_pending_frames+0x12d/0x260 net/ipv4/ip_output.c:1545
>   udp_flush_pending_frames net/ipv4/udp.c:829 [inline]
>   udp_sendmsg+0x5d2/0x2a50 net/ipv4/udp.c:1302
>   sock_sendmsg_nosec net/socket.c:729 [inline]
>   __sock_sendmsg+0x1a6/0x270 net/socket.c:744
>   sock_sendmsg+0x134/0x200 net/socket.c:767
>   splice_to_socket+0xa10/0x10b0 fs/splice.c:889
>   do_splice_from fs/splice.c:941 [inline]
>   direct_splice_actor+0x11b/0x220 fs/splice.c:1164
>   splice_direct_to_actor+0x586/0xc80 fs/splice.c:1108
>   do_splice_direct_actor fs/splice.c:1207 [inline]
>   do_splice_direct+0x289/0x3e0 fs/splice.c:1233
>   do_sendfile+0x561/0xe10 fs/read_write.c:1388
>   __do_sys_sendfile64 fs/read_write.c:1455 [inline]
>   __se_sys_sendfile64+0x17c/0x1e0 fs/read_write.c:1441
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f17eb533ab9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 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:00007ffdeb190c28 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f17eb533ab9
> RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000004
> RBP: 00007f17eb5a65f0 R08: 0000000000000006 R09: 0000000000000006
> R10: 0000020000023893 R11: 0000000000000246 R12: 0000000000000001
> R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
>  </TASK>
> 
> [...]

Applied, thanks!

[1/1] iov-iter: do not return more bytes than requested in iov_iter_extract_bvec_pages()
      commit: 7bc802acf193010c5b2afb88523a57766b836bc1

Best regards,
-- 
Jens Axboe