Lin Ma 361b6889ae net/handshake: remove fput() that causes use-after-free ... A reference underflow is found in TLS handshake subsystem that causes a direct use-after-free. Part of the crash log is like below: [ 2.022114] ------------[ cut here ]------------ [ 2.022193] refcount_t: underflow; use-after-free. [ 2.022288] WARNING: CPU: 0 PID: 60 at lib/refcount.c:28 refcount_warn_saturate+0xbe/0x110 [ 2.022432] Modules linked in: [ 2.022848] RIP: 0010:refcount_warn_saturate+0xbe/0x110 [ 2.023231] RSP: 0018:ffffc900001bfe18 EFLAGS: 00000286 [ 2.023325] RAX: 0000000000000000 RBX: 0000000000000007 RCX: 00000000ffffdfff [ 2.023438] RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001 [ 2.023555] RBP: ffff888004c20098 R08: ffffffff82b392c8 R09: 00000000ffffdfff [ 2.023693] R10: ffffffff82a592e0 R11: ffffffff82b092e0 R12: ffff888004c200d8 [ 2.023813] R13: 0000000000000000 R14: ffff888004c20000 R15: ffffc90000013ca8 [ 2.023930] FS: 0000000000000000(0000) GS:ffff88807dc00000(0000) knlGS:0000000000000000 [ 2.024062] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 2.024161] CR2: ffff888003601000 CR3: 0000000002a2e000 CR4: 00000000000006f0 [ 2.024275] Call Trace: [ 2.024322] <TASK> [ 2.024367] ? __warn+0x7f/0x130 [ 2.024430] ? refcount_warn_saturate+0xbe/0x110 [ 2.024513] ? report_bug+0x199/0x1b0 [ 2.024585] ? handle_bug+0x3c/0x70 [ 2.024676] ? exc_invalid_op+0x18/0x70 [ 2.024750] ? asm_exc_invalid_op+0x1a/0x20 [ 2.024830] ? refcount_warn_saturate+0xbe/0x110 [ 2.024916] ? refcount_warn_saturate+0xbe/0x110 [ 2.024998] __tcp_close+0x2f4/0x3d0 [ 2.025065] ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 [ 2.025168] tcp_close+0x1f/0x70 [ 2.025231] inet_release+0x33/0x60 [ 2.025297] sock_release+0x1f/0x80 [ 2.025361] handshake_req_cancel_test2+0x100/0x2d0 [ 2.025457] kunit_try_run_case+0x4c/0xa0 [ 2.025532] kunit_generic_run_threadfn_adapter+0x15/0x20 [ 2.025644] kthread+0xe1/0x110 [ 2.025708] ? __pfx_kthread+0x10/0x10 [ 2.025780] ret_from_fork+0x2c/0x50 One can enable CONFIG_NET_HANDSHAKE_KUNIT_TEST config to reproduce above crash. The root cause of this bug is that the commit 1ce77c998f ("net/handshake: Unpin sock->file if a handshake is cancelled") adds one additional fput() function. That patch claims that the fput() is used to enable sock->file to be freed even when user space never calls DONE. However, it seems that the intended DONE routine will never give an additional fput() of ths sock->file. The existing two of them are just used to balance the reference added in sockfd_lookup(). This patch revert the mentioned commit to avoid the use-after-free. The patched kernel could successfully pass the KUNIT test and boot to shell. [ 0.733613] # Subtest: Handshake API tests [ 0.734029] 1..11 [ 0.734255] KTAP version 1 [ 0.734542] # Subtest: req_alloc API fuzzing [ 0.736104] ok 1 handshake_req_alloc NULL proto [ 0.736114] ok 2 handshake_req_alloc CLASS_NONE [ 0.736559] ok 3 handshake_req_alloc CLASS_MAX [ 0.737020] ok 4 handshake_req_alloc no callbacks [ 0.737488] ok 5 handshake_req_alloc no done callback [ 0.737988] ok 6 handshake_req_alloc excessive privsize [ 0.738529] ok 7 handshake_req_alloc all good [ 0.739036] # req_alloc API fuzzing: pass:7 fail:0 skip:0 total:7 [ 0.739444] ok 1 req_alloc API fuzzing [ 0.740065] ok 2 req_submit NULL req arg [ 0.740436] ok 3 req_submit NULL sock arg [ 0.740834] ok 4 req_submit NULL sock->file [ 0.741236] ok 5 req_lookup works [ 0.741621] ok 6 req_submit max pending [ 0.741974] ok 7 req_submit multiple [ 0.742382] ok 8 req_cancel before accept [ 0.742764] ok 9 req_cancel after accept [ 0.743151] ok 10 req_cancel after done [ 0.743510] ok 11 req_destroy works [ 0.743882] # Handshake API tests: pass:11 fail:0 skip:0 total:11 [ 0.744205] # Totals: pass:17 fail:0 skip:0 total:17 Acked-by: Chuck Lever <chuck.lever@oracle.com> Fixes: 1ce77c998f ("net/handshake: Unpin sock->file if a handshake is cancelled") Signed-off-by: Lin Ma <linma@zju.edu.cn> Link: https://lore.kernel.org/r/20230613083204.633896-1-linma@zju.edu.cn Link: https://lore.kernel.org/r/20230614015249.987448-1-linma@zju.edu.cn Signed-off-by: Jakub Kicinski <kuba@kernel.org>		2023-06-14 22:26:37 -07:00
..
.kunitconfig	net/handshake: Add Kunit tests for the handshake consumer API	2023-04-19 18:48:48 -07:00
genl.c
genl.h
handshake-test.c	net/handshake: Fix sock->file allocation	2023-05-22 19:25:24 -07:00
handshake.h	net/handshake: remove fput() that causes use-after-free	2023-06-14 22:26:37 -07:00
Makefile	net/handshake: Add Kunit tests for the handshake consumer API	2023-04-19 18:48:48 -07:00
netlink.c	net/handshake: handshake_genl_notify() shouldn't ignore @flags	2023-05-24 22:05:24 -07:00
request.c	net/handshake: remove fput() that causes use-after-free	2023-06-14 22:26:37 -07:00
tlshd.c	net/handshake: Enable the SNI extension to work properly	2023-05-24 22:05:24 -07:00
trace.c