4.20-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 9060cb719e61b685ec0102574e10337fa5f445ea ]
KASAN has found use-after-free in sockfs_setattr. The existed commit 6d8c50dcb029 ("socket: close race condition between sock_close() and sockfs_setattr()") is to fix this simillar issue, but it seems to ignore that crypto module forgets to set the sk to NULL after af_alg_release.
KASAN report details as below: BUG: KASAN: use-after-free in sockfs_setattr+0x120/0x150 Write of size 4 at addr ffff88837b956128 by task syz-executor0/4186
CPU: 2 PID: 4186 Comm: syz-executor0 Not tainted xxx + #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 Call Trace: dump_stack+0xca/0x13e print_address_description+0x79/0x330 ? vprintk_func+0x5e/0xf0 kasan_report+0x18a/0x2e0 ? sockfs_setattr+0x120/0x150 sockfs_setattr+0x120/0x150 ? sock_register+0x2d0/0x2d0 notify_change+0x90c/0xd40 ? chown_common+0x2ef/0x510 chown_common+0x2ef/0x510 ? chmod_common+0x3b0/0x3b0 ? __lock_is_held+0xbc/0x160 ? __sb_start_write+0x13d/0x2b0 ? __mnt_want_write+0x19a/0x250 do_fchownat+0x15c/0x190 ? __ia32_sys_chmod+0x80/0x80 ? trace_hardirqs_on_thunk+0x1a/0x1c __x64_sys_fchownat+0xbf/0x160 ? lockdep_hardirqs_on+0x39a/0x5e0 do_syscall_64+0xc8/0x580 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x462589 Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 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 bc ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fb4b2c83c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000104 RAX: ffffffffffffffda RBX: 000000000072bfa0 RCX: 0000000000462589 RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000007 RBP: 0000000000000005 R08: 0000000000001000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb4b2c846bc R13: 00000000004bc733 R14: 00000000006f5138 R15: 00000000ffffffff
Allocated by task 4185: kasan_kmalloc+0xa0/0xd0 __kmalloc+0x14a/0x350 sk_prot_alloc+0xf6/0x290 sk_alloc+0x3d/0xc00 af_alg_accept+0x9e/0x670 hash_accept+0x4a3/0x650 __sys_accept4+0x306/0x5c0 __x64_sys_accept4+0x98/0x100 do_syscall_64+0xc8/0x580 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Freed by task 4184: __kasan_slab_free+0x12e/0x180 kfree+0xeb/0x2f0 __sk_destruct+0x4e6/0x6a0 sk_destruct+0x48/0x70 __sk_free+0xa9/0x270 sk_free+0x2a/0x30 af_alg_release+0x5c/0x70 __sock_release+0xd3/0x280 sock_close+0x1a/0x20 __fput+0x27f/0x7f0 task_work_run+0x136/0x1b0 exit_to_usermode_loop+0x1a7/0x1d0 do_syscall_64+0x461/0x580 entry_SYSCALL_64_after_hwframe+0x49/0xbe
Syzkaller reproducer: r0 = perf_event_open(&(0x7f0000000000)={0x0, 0x70, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, @perf_config_ext}, 0x0, 0x0, 0xffffffffffffffff, 0x0) r1 = socket$alg(0x26, 0x5, 0x0) getrusage(0x0, 0x0) bind(r1, &(0x7f00000001c0)=@alg={0x26, 'hash\x00', 0x0, 0x0, 'sha256-ssse3\x00'}, 0x80) r2 = accept(r1, 0x0, 0x0) r3 = accept4$unix(r2, 0x0, 0x0, 0x0) r4 = dup3(r3, r0, 0x0) fchownat(r4, &(0x7f00000000c0)='\x00', 0x0, 0x0, 0x1000)
Fixes: 6d8c50dcb029 ("socket: close race condition between sock_close() and sockfs_setattr()") Signed-off-by: Mao Wenan maowenan@huawei.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- crypto/af_alg.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/crypto/af_alg.c b/crypto/af_alg.c index 17eb09d222ff4..ec78a04eb136e 100644 --- a/crypto/af_alg.c +++ b/crypto/af_alg.c @@ -122,8 +122,10 @@ static void alg_do_release(const struct af_alg_type *type, void *private)
int af_alg_release(struct socket *sock) { - if (sock->sk) + if (sock->sk) { sock_put(sock->sk); + sock->sk = NULL; + } return 0; } EXPORT_SYMBOL_GPL(af_alg_release);