Re: memory leak in sctp_stream_init_ext

[Xin Long]

On Fri, May 31, 2019 at 10:59 PM syzbot
<syzbot+7f3b6b106be8dcdcdeec@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    bec7550c Merge tag 'docs-5.2-fixes2' of git://git.lwn.net/..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=152a0916a00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=64479170dcaf0e11
> dashboard link: https://syzkaller.appspot.com/bug?extid=7f3b6b106be8dcdcdeec
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1142cd4ca00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f81d72a00000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+7f3b6b106be8dcdcdeec@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> executing program
> executing program
> executing program
> executing program
> executing program
> BUG: memory leak
> unreferenced object 0xffff8881114f5d80 (size 96):
>    comm "syz-executor934", pid 7160, jiffies 4294993058 (age 31.950s)
>    hex dump (first 32 bytes):
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>    backtrace:
>      [<00000000ce7a1326>] kmemleak_alloc_recursive
> include/linux/kmemleak.h:55 [inline]
>      [<00000000ce7a1326>] slab_post_alloc_hook mm/slab.h:439 [inline]
>      [<00000000ce7a1326>] slab_alloc mm/slab.c:3326 [inline]
>      [<00000000ce7a1326>] kmem_cache_alloc_trace+0x13d/0x280 mm/slab.c:3553
>      [<000000007abb7ac9>] kmalloc include/linux/slab.h:547 [inline]
>      [<000000007abb7ac9>] kzalloc include/linux/slab.h:742 [inline]
>      [<000000007abb7ac9>] sctp_stream_init_ext+0x2b/0xa0
> net/sctp/stream.c:157
>      [<0000000048ecb9c1>] sctp_sendmsg_to_asoc+0x946/0xa00
> net/sctp/socket.c:1882

is this possible to be a false positive?

As in my testing, I tracked the objects allocated by
"sctp_sendmsg_to_asoc () -> sctp_stream_init_ext()."
all of them got freed properly in sctp_stream_free(),
while this warning was still triggered.

>      [<000000004483ca2b>] sctp_sendmsg+0x2a8/0x990 net/sctp/socket.c:2102
>      [<0000000094bdc32e>] inet_sendmsg+0x64/0x120 net/ipv4/af_inet.c:802
>      [<0000000022d1c2a5>] sock_sendmsg_nosec net/socket.c:652 [inline]
>      [<0000000022d1c2a5>] sock_sendmsg+0x54/0x70 net/socket.c:671
>      [<000000006ab53119>] sock_write_iter+0xb6/0x130 net/socket.c:1000
>      [<00000000973772ef>] call_write_iter include/linux/fs.h:1872 [inline]
>      [<00000000973772ef>] new_sync_write+0x1ad/0x260 fs/read_write.c:483
>      [<0000000033f2491b>] __vfs_write+0x87/0xa0 fs/read_write.c:496
>      [<00000000372fbd56>] vfs_write fs/read_write.c:558 [inline]
>      [<00000000372fbd56>] vfs_write+0xee/0x210 fs/read_write.c:542
>      [<000000007ccb2ea5>] ksys_write+0x7c/0x130 fs/read_write.c:611
>      [<000000001c29b8c7>] __do_sys_write fs/read_write.c:623 [inline]
>      [<000000001c29b8c7>] __se_sys_write fs/read_write.c:620 [inline]
>      [<000000001c29b8c7>] __x64_sys_write+0x1e/0x30 fs/read_write.c:620
>      [<0000000014d9243b>] do_syscall_64+0x76/0x1a0
> arch/x86/entry/common.c:301
>      [<0000000059f6e9a8>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> BUG: memory leak
> unreferenced object 0xffff8881114f5d80 (size 96):
>    comm "syz-executor934", pid 7160, jiffies 4294993058 (age 33.160s)
>    hex dump (first 32 bytes):
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>    backtrace:
>      [<00000000ce7a1326>] kmemleak_alloc_recursive
> include/linux/kmemleak.h:55 [inline]
>      [<00000000ce7a1326>] slab_post_alloc_hook mm/slab.h:439 [inline]
>      [<00000000ce7a1326>] slab_alloc mm/slab.c:3326 [inline]
>      [<00000000ce7a1326>] kmem_cache_alloc_trace+0x13d/0x280 mm/slab.c:3553
>      [<000000007abb7ac9>] kmalloc include/linux/slab.h:547 [inline]
>      [<000000007abb7ac9>] kzalloc include/linux/slab.h:742 [inline]
>      [<000000007abb7ac9>] sctp_stream_init_ext+0x2b/0xa0
> net/sctp/stream.c:157
>      [<0000000048ecb9c1>] sctp_sendmsg_to_asoc+0x946/0xa00
> net/sctp/socket.c:1882
>      [<000000004483ca2b>] sctp_sendmsg+0x2a8/0x990 net/sctp/socket.c:2102
>      [<0000000094bdc32e>] inet_sendmsg+0x64/0x120 net/ipv4/af_inet.c:802
>      [<0000000022d1c2a5>] sock_sendmsg_nosec net/socket.c:652 [inline]
>      [<0000000022d1c2a5>] sock_sendmsg+0x54/0x70 net/socket.c:671
>      [<000000006ab53119>] sock_write_iter+0xb6/0x130 net/socket.c:1000
>      [<00000000973772ef>] call_write_iter include/linux/fs.h:1872 [inline]
>      [<00000000973772ef>] new_sync_write+0x1ad/0x260 fs/read_write.c:483
>      [<0000000033f2491b>] __vfs_write+0x87/0xa0 fs/read_write.c:496
>      [<00000000372fbd56>] vfs_write fs/read_write.c:558 [inline]
>      [<00000000372fbd56>] vfs_write+0xee/0x210 fs/read_write.c:542
>      [<000000007ccb2ea5>] ksys_write+0x7c/0x130 fs/read_write.c:611
>      [<000000001c29b8c7>] __do_sys_write fs/read_write.c:623 [inline]
>      [<000000001c29b8c7>] __se_sys_write fs/read_write.c:620 [inline]
>      [<000000001c29b8c7>] __x64_sys_write+0x1e/0x30 fs/read_write.c:620
>      [<0000000014d9243b>] do_syscall_64+0x76/0x1a0
> arch/x86/entry/common.c:301
>      [<0000000059f6e9a8>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> executing program
> executing program
> executing program
> executing program
> executing program
> executing program
>
>
> ---
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