Re: [PATCH v3] net/smc: fix refcount bug in sk_psock_get (2)

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





On 2022/8/3 16:03, Hawkins Jiawei wrote:
Syzkaller reports refcount bug as follows:
------------[ cut here ]------------
refcount_t: saturated; leaking memory.
WARNING: CPU: 1 PID: 3605 at lib/refcount.c:19 refcount_warn_saturate+0xf4/0x1e0 lib/refcount.c:19
Modules linked in:
CPU: 1 PID: 3605 Comm: syz-executor208 Not tainted 5.18.0-syzkaller-03023-g7e062cda7d90 #0
  <TASK>
  __refcount_add_not_zero include/linux/refcount.h:163 [inline]
  __refcount_inc_not_zero include/linux/refcount.h:227 [inline]
  refcount_inc_not_zero include/linux/refcount.h:245 [inline]
  sk_psock_get+0x3bc/0x410 include/linux/skmsg.h:439
  tls_data_ready+0x6d/0x1b0 net/tls/tls_sw.c:2091
  tcp_data_ready+0x106/0x520 net/ipv4/tcp_input.c:4983
  tcp_data_queue+0x25f2/0x4c90 net/ipv4/tcp_input.c:5057
  tcp_rcv_state_process+0x1774/0x4e80 net/ipv4/tcp_input.c:6659
  tcp_v4_do_rcv+0x339/0x980 net/ipv4/tcp_ipv4.c:1682
  sk_backlog_rcv include/net/sock.h:1061 [inline]
  __release_sock+0x134/0x3b0 net/core/sock.c:2849
  release_sock+0x54/0x1b0 net/core/sock.c:3404
  inet_shutdown+0x1e0/0x430 net/ipv4/af_inet.c:909
  __sys_shutdown_sock net/socket.c:2331 [inline]
  __sys_shutdown_sock net/socket.c:2325 [inline]
  __sys_shutdown+0xf1/0x1b0 net/socket.c:2343
  __do_sys_shutdown net/socket.c:2351 [inline]
  __se_sys_shutdown net/socket.c:2349 [inline]
  __x64_sys_shutdown+0x50/0x70 net/socket.c:2349
  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
  do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
  entry_SYSCALL_64_after_hwframe+0x46/0xb0
  </TASK>

During SMC fallback process in connect syscall, kernel will
replaces TCP with SMC. In order to forward wakeup
smc socket waitqueue after fallback, kernel will sets
clcsk->sk_user_data to origin smc socket in
smc_fback_replace_callbacks().

Later, in shutdown syscall, kernel will calls
sk_psock_get(), which treats the clcsk->sk_user_data
as psock type, triggering the refcnt warning.

So, the root cause is that smc and psock, both will use
sk_user_data field. So they will mismatch this field
easily.

This patch solves it by using another bit(defined as
SK_USER_DATA_PSOCK) in PTRMASK, to mark whether
sk_user_data points to a psock object or not.
This patch depends on a PTRMASK introduced in commit f1ff5ce2cd5e
("net, sk_msg: Clear sk_user_data pointer on clone if tagged").

Reported-and-tested-by: syzbot+5f26f85569bd179c18ce@xxxxxxxxxxxxxxxxxxxxxxxxx
Suggested-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Acked-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
Signed-off-by: Hawkins Jiawei <yin31149@xxxxxxxxx>
---
v2 -> v3:
   - use SK_USER_DATA_PSOCK instead of SK_USER_DATA_NOTPSOCK
to patch the bug
   - refactor the code on assigning to sk_user_data field
in psock part
   - refactor the code on getting and setting the flag
with sk_user_data field

v1 -> v2:
   - add bit in PTRMASK to patch the bug

  include/linux/skmsg.h |  2 +-
  include/net/sock.h    | 58 +++++++++++++++++++++++++++++++------------
  net/core/skmsg.c      |  3 ++-
  3 files changed, 45 insertions(+), 18 deletions(-)


Hi Hawkins,

Since the fix v3 doesn't involved smc codes any more, I wonder if it's still
appropriate to use 'net/smc:' in subject?

Cheers,
Wen Gu



[Index of Archives]     [Linux Samsung SoC]     [Linux Rockchip SoC]     [Linux Actions SoC]     [Linux for Synopsys ARC Processors]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]


  Powered by Linux