On 05/22/2019 12:01 PM, Jakub Sitnicki wrote: > Once psock gets unlinked from its sock (sk_psock_drop), user-space can > still trigger a call to sk->sk_write_space by setting TCP_NOTSENT_LOWAT > socket option. This causes a null-ptr-deref because we try to read > psock->saved_write_space from sk_psock_write_space: > > ================================================================== > BUG: KASAN: null-ptr-deref in sk_psock_write_space+0x69/0x80 > Read of size 8 at addr 00000000000001a0 by task sockmap-echo/131 > > CPU: 0 PID: 131 Comm: sockmap-echo Not tainted 5.2.0-rc1-00094-gf49aa1de9836 #81 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS > ?-20180724_192412-buildhw-07.phx2.fedoraproject.org-1.fc29 04/01/2014 > Call Trace: > ? sk_psock_write_space+0x69/0x80 > __kasan_report.cold.2+0x5/0x3f > ? sk_psock_write_space+0x69/0x80 > kasan_report+0xe/0x20 > sk_psock_write_space+0x69/0x80 > tcp_setsockopt+0x69a/0xfc0 > ? tcp_shutdown+0x70/0x70 > ? fsnotify+0x5b0/0x5f0 > ? remove_wait_queue+0x90/0x90 > ? __fget_light+0xa5/0xf0 > __sys_setsockopt+0xe6/0x180 > ? sockfd_lookup_light+0xb0/0xb0 > ? vfs_write+0x195/0x210 > ? ksys_write+0xc9/0x150 > ? __x64_sys_read+0x50/0x50 > ? __bpf_trace_x86_fpu+0x10/0x10 > __x64_sys_setsockopt+0x61/0x70 > do_syscall_64+0xc5/0x520 > ? vmacache_find+0xc0/0x110 > ? syscall_return_slowpath+0x110/0x110 > ? handle_mm_fault+0xb4/0x110 > ? entry_SYSCALL_64_after_hwframe+0x3e/0xbe > ? trace_hardirqs_off_caller+0x4b/0x120 > ? trace_hardirqs_off_thunk+0x1a/0x3a > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x7f2e5e7cdcce > Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb b1 66 2e 0f 1f 84 00 00 00 00 00 > 0f 1f 44 00 00 f3 0f 1e fa 49 89 ca b8 36 00 00 00 0f 05 <48> 3d 01 f0 ff > ff 73 01 c3 48 8b 0d 8a 11 0c 00 f7 d8 64 89 01 48 > RSP: 002b:00007ffed011b778 EFLAGS: 00000206 ORIG_RAX: 0000000000000036 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f2e5e7cdcce > RDX: 0000000000000019 RSI: 0000000000000006 RDI: 0000000000000007 > RBP: 00007ffed011b790 R08: 0000000000000004 R09: 00007f2e5e84ee80 > R10: 00007ffed011b788 R11: 0000000000000206 R12: 00007ffed011b78c > R13: 00007ffed011b788 R14: 0000000000000007 R15: 0000000000000068 > ================================================================== > > Restore the saved sk_write_space callback when psock is being dropped to > fix the crash. > > Signed-off-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx> LGTM, applied thanks!
