@@ -2673,7 +2673,8 @@ static struct sk_buff *manage_oob(struct sk_buff *skb, struct sock *sk,
__skb_unlink(read_skb, &sk->sk_receive_queue);
}
- goto unlock;
+ if (!skb)
+ goto unlock;
}
if (skb != u->oob_skb)
@@ -3175,9 +3176,13 @@ static int unix_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
skb = skb_peek(&sk->sk_receive_queue);
if (skb) {
struct sk_buff *oob_skb = READ_ONCE(u->oob_skb);
+ struct sk_buff *next_skb;
+
+ next_skb = skb_peek_next(skb, &sk->sk_receive_queue);
if (skb == oob_skb ||
- (!oob_skb && !unix_skb_len(skb)))
+ (!unix_skb_len(skb) &&
+ (!oob_skb || next_skb == oob_skb)))
answ = 1;
}
@@ -525,6 +525,29 @@ TEST_F(msg_oob, ex_oob_drop_2)
}
}
+TEST_F(msg_oob, ex_oob_oob)
+{
+ sendpair("x", 1, MSG_OOB);
+ epollpair(true);
+ siocatmarkpair(true);
+
+ recvpair("x", 1, 1, MSG_OOB);
+ epollpair(false);
+ siocatmarkpair(true);
+
+ sendpair("y", 1, MSG_OOB);
+ epollpair(true);
+ siocatmarkpair(true);
+
+ recvpair("", -EAGAIN, 1, 0);
+ epollpair(false);
+ siocatmarkpair(false);
+
+ recvpair("", -EINVAL, 1, MSG_OOB);
+ epollpair(false);
+ siocatmarkpair(false);
+}
+
TEST_F(msg_oob, ex_oob_ahead_break)
{
sendpair("hello", 5, MSG_OOB);
syzbot reported use-after-free in unix_stream_recv_urg(). [0] The scenario is 1. send(MSG_OOB) 2. recv(MSG_OOB) -> The consumed OOB remains in recv queue 3. send(MSG_OOB) 4. recv() -> manage_oob() returns the next skb of the consumed OOB -> This is also OOB, but unix_sk(sk)->oob_skb is not cleared 5. recv(MSG_OOB) -> unix_sk(sk)->oob_skb is used but already freed The recent commit 8594d9b85c07 ("af_unix: Don't call skb_get() for OOB skb.") uncovered the issue. If the OOB skb is consumed and the next skb is peeked in manage_oob(), we still need to check if the skb is OOB. Let's do so by falling back to the following checks in manage_oob() and add the test case in selftest. Note that we need to add a similar check for SIOCATMARK. [0]: BUG: KASAN: slab-use-after-free in unix_stream_read_actor+0xa6/0xb0 net/unix/af_unix.c:2959 Read of size 4 at addr ffff8880326abcc4 by task syz-executor178/5235 CPU: 0 UID: 0 PID: 5235 Comm: syz-executor178 Not tainted 6.11.0-rc5-syzkaller-00742-gfbdaffe41adc #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 Call Trace: <TASK> __dump_stack lib/dump_stack.c:93 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119 print_address_description mm/kasan/report.c:377 [inline] print_report+0x169/0x550 mm/kasan/report.c:488 kasan_report+0x143/0x180 mm/kasan/report.c:601 unix_stream_read_actor+0xa6/0xb0 net/unix/af_unix.c:2959 unix_stream_recv_urg+0x1df/0x320 net/unix/af_unix.c:2640 unix_stream_read_generic+0x2456/0x2520 net/unix/af_unix.c:2778 unix_stream_recvmsg+0x22b/0x2c0 net/unix/af_unix.c:2996 sock_recvmsg_nosec net/socket.c:1046 [inline] sock_recvmsg+0x22f/0x280 net/socket.c:1068 ____sys_recvmsg+0x1db/0x470 net/socket.c:2816 ___sys_recvmsg net/socket.c:2858 [inline] __sys_recvmsg+0x2f0/0x3e0 net/socket.c:2888 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f5360d6b4e9 Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fff29b3a458 EFLAGS: 00000246 ORIG_RAX: 000000000000002f RAX: ffffffffffffffda RBX: 00007fff29b3a638 RCX: 00007f5360d6b4e9 RDX: 0000000000002001 RSI: 0000000020000640 RDI: 0000000000000003 RBP: 00007f5360dde610 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007fff29b3a628 R14: 0000000000000001 R15: 0000000000000001 </TASK> Allocated by task 5235: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 unpoison_slab_object mm/kasan/common.c:312 [inline] __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338 kasan_slab_alloc include/linux/kasan.h:201 [inline] slab_post_alloc_hook mm/slub.c:3988 [inline] slab_alloc_node mm/slub.c:4037 [inline] kmem_cache_alloc_node_noprof+0x16b/0x320 mm/slub.c:4080 __alloc_skb+0x1c3/0x440 net/core/skbuff.c:667 alloc_skb include/linux/skbuff.h:1320 [inline] alloc_skb_with_frags+0xc3/0x770 net/core/skbuff.c:6528 sock_alloc_send_pskb+0x91a/0xa60 net/core/sock.c:2815 sock_alloc_send_skb include/net/sock.h:1778 [inline] queue_oob+0x108/0x680 net/unix/af_unix.c:2198 unix_stream_sendmsg+0xd24/0xf80 net/unix/af_unix.c:2351 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg+0x221/0x270 net/socket.c:745 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2597 ___sys_sendmsg net/socket.c:2651 [inline] __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2680 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 5235: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579 poison_slab_object+0xe0/0x150 mm/kasan/common.c:240 __kasan_slab_free+0x37/0x60 mm/kasan/common.c:256 kasan_slab_free include/linux/kasan.h:184 [inline] slab_free_hook mm/slub.c:2252 [inline] slab_free mm/slub.c:4473 [inline] kmem_cache_free+0x145/0x350 mm/slub.c:4548 unix_stream_read_generic+0x1ef6/0x2520 net/unix/af_unix.c:2917 unix_stream_recvmsg+0x22b/0x2c0 net/unix/af_unix.c:2996 sock_recvmsg_nosec net/socket.c:1046 [inline] sock_recvmsg+0x22f/0x280 net/socket.c:1068 __sys_recvfrom+0x256/0x3e0 net/socket.c:2255 __do_sys_recvfrom net/socket.c:2273 [inline] __se_sys_recvfrom net/socket.c:2269 [inline] __x64_sys_recvfrom+0xde/0x100 net/socket.c:2269 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff8880326abc80 which belongs to the cache skbuff_head_cache of size 240 The buggy address is located 68 bytes inside of freed 240-byte region [ffff8880326abc80, ffff8880326abd70) The buggy address belongs to the physical page: page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x326ab ksm flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff) page_type: 0xfdffffff(slab) raw: 00fff00000000000 ffff88801eaee780 ffffea0000b7dc80 dead000000000003 raw: 0000000000000000 00000000800c000c 00000001fdffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 4686, tgid 4686 (udevadm), ts 32357469485, free_ts 28829011109 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1493 prep_new_page mm/page_alloc.c:1501 [inline] get_page_from_freelist+0x2e4c/0x2f10 mm/page_alloc.c:3439 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4695 __alloc_pages_node_noprof include/linux/gfp.h:269 [inline] alloc_pages_node_noprof include/linux/gfp.h:296 [inline] alloc_slab_page+0x5f/0x120 mm/slub.c:2321 allocate_slab+0x5a/0x2f0 mm/slub.c:2484 new_slab mm/slub.c:2537 [inline] ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3723 __slab_alloc+0x58/0xa0 mm/slub.c:3813 __slab_alloc_node mm/slub.c:3866 [inline] slab_alloc_node mm/slub.c:4025 [inline] kmem_cache_alloc_node_noprof+0x1fe/0x320 mm/slub.c:4080 __alloc_skb+0x1c3/0x440 net/core/skbuff.c:667 alloc_skb include/linux/skbuff.h:1320 [inline] alloc_uevent_skb+0x74/0x230 lib/kobject_uevent.c:289 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline] kobject_uevent_net_broadcast+0x2fd/0x580 lib/kobject_uevent.c:410 kobject_uevent_env+0x57d/0x8e0 lib/kobject_uevent.c:608 kobject_synth_uevent+0x4ef/0xae0 lib/kobject_uevent.c:207 uevent_store+0x4b/0x70 drivers/base/bus.c:633 kernfs_fop_write_iter+0x3a1/0x500 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:497 [inline] vfs_write+0xa72/0xc90 fs/read_write.c:590 page last free pid 1 tgid 1 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] free_pages_prepare mm/page_alloc.c:1094 [inline] free_unref_page+0xd22/0xea0 mm/page_alloc.c:2612 kasan_depopulate_vmalloc_pte+0x74/0x90 mm/kasan/shadow.c:408 apply_to_pte_range mm/memory.c:2797 [inline] apply_to_pmd_range mm/memory.c:2841 [inline] apply_to_pud_range mm/memory.c:2877 [inline] apply_to_p4d_range mm/memory.c:2913 [inline] __apply_to_page_range+0x8a8/0xe50 mm/memory.c:2947 kasan_release_vmalloc+0x9a/0xb0 mm/kasan/shadow.c:525 purge_vmap_node+0x3e3/0x770 mm/vmalloc.c:2208 __purge_vmap_area_lazy+0x708/0xae0 mm/vmalloc.c:2290 _vm_unmap_aliases+0x79d/0x840 mm/vmalloc.c:2885 change_page_attr_set_clr+0x2fe/0xdb0 arch/x86/mm/pat/set_memory.c:1881 change_page_attr_set arch/x86/mm/pat/set_memory.c:1922 [inline] set_memory_nx+0xf2/0x130 arch/x86/mm/pat/set_memory.c:2110 free_init_pages arch/x86/mm/init.c:924 [inline] free_kernel_image_pages arch/x86/mm/init.c:943 [inline] free_initmem+0x79/0x110 arch/x86/mm/init.c:970 kernel_init+0x31/0x2b0 init/main.c:1476 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 Memory state around the buggy address: ffff8880326abb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880326abc00: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc >ffff8880326abc80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880326abd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc ffff8880326abd80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb Fixes: 93c99f21db36 ("af_unix: Don't stop recv(MSG_DONTWAIT) if consumed OOB skb is at the head.") Reported-by: syzbot+8811381d455e3e9ec788@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=8811381d455e3e9ec788 Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- net/unix/af_unix.c | 9 ++++++-- tools/testing/selftests/net/af_unix/msg_oob.c | 23 +++++++++++++++++++ 2 files changed, 30 insertions(+), 2 deletions(-)