syzbot found the following crash on:

HEAD commit:    036e3431 Merge git://git.kernel.org/pub/scm/linux/kernel/g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=153cff12a00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8f0f63a62bb5b13c
dashboard link: https://syzkaller.appspot.com/bug?extid=6ad9c3bd0a218a2ab41d
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12561c86a00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15b76fd8a00000

executing program
executing program
executing program
executing program
executing program
BUG: memory leak
unreferenced object 0xffff888123894820 (size 32):
  comm "syz-executor045", pid 7267, jiffies 4294943559 (age 13.660s)
  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:
    [<00000000c7e71c69>] kmemleak_alloc_recursive
include/linux/kmemleak.h:55 [inline]
    [<00000000c7e71c69>] slab_post_alloc_hook mm/slab.h:439 [inline]
    [<00000000c7e71c69>] slab_alloc mm/slab.c:3326 [inline]
    [<00000000c7e71c69>] __do_kmalloc mm/slab.c:3658 [inline]
    [<00000000c7e71c69>] __kmalloc+0x161/0x2c0 mm/slab.c:3669
    [<000000003250ed8e>] kmalloc_array include/linux/slab.h:670 [inline]
    [<000000003250ed8e>] kcalloc include/linux/slab.h:681 [inline]
    [<000000003250ed8e>] sctp_send_reset_streams+0x1ab/0x5a0 net/sctp/stream.c:302
    [<00000000cd899c6e>] sctp_setsockopt_reset_streams net/sctp/socket.c:4314 [inline]
    [<00000000cd899c6e>] sctp_setsockopt net/sctp/socket.c:4765 [inline]
    [<00000000cd899c6e>] sctp_setsockopt+0xc23/0x2bf0 net/sctp/socket.c:4608
    [<00000000ff3a21a2>] sock_common_setsockopt+0x38/0x50 net/core/sock.c:3130
    [<000000009eb87ae7>] __sys_setsockopt+0x98/0x120 net/socket.c:2078
    [<00000000e0ede6ca>] __do_sys_setsockopt net/socket.c:2089 [inline]
    [<00000000e0ede6ca>] __se_sys_setsockopt net/socket.c:2086 [inline]
    [<00000000e0ede6ca>] __x64_sys_setsockopt+0x26/0x30 net/socket.c:2086
    [<00000000c61155f5>] do_syscall_64+0x76/0x1a0 arch/x86/entry/common.c:301
    [<00000000e540958c>] entry_SYSCALL_64_after_hwframe+0x44/0xa9


It was introduced in commit d570a59c5b5f ("sctp: only allow the out stream
reset when the stream outq is empty"), in orde to check stream outqs before
sending SCTP_STRRESET_IN_PROGRESS back to the peer of the stream. EAGAIN is
returned, however, without the nstr_list slab released, if any outq is found
to be non empty.

Freeing the slab in question before bailing out fixes it.

Fixes: d570a59c5b5f ("sctp: only allow the out stream reset when the stream outq is empty")
Reported-by: syzbot <redacted>
Reported-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Tested-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Cc: Xin Long <lucien.xin@gmail.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: Vlad Yasevich <redacted>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Hillf Danton <redacted>
---
net/sctp/stream.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index 93ed078..d3e2f03 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c

@@ -310,6 +310,7 @@ int sctp_send_reset_streams(struct sctp_association *asoc,

	if (out && !sctp_stream_outq_is_empty(stream, str_nums, nstr_list)) {
		retval = -EAGAIN;
+		kfree(nstr_list);
		goto out;
	}

--