From: Tuong Lien tuong.t.lien@dektech.com.au
[ Upstream commit 5e9eeccc58f3e6bcc99b929670665d2ce047e9c9 ]
syzbot found the following crash:
general protection fault, probably for non-canonical address 0xdffffc0000000019: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x00000000000000c8-0x00000000000000cf] CPU: 1 PID: 7060 Comm: syz-executor394 Not tainted 5.7.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:__tipc_sendstream+0xbde/0x11f0 net/tipc/socket.c:1591 Code: 00 00 00 00 48 39 5c 24 28 48 0f 44 d8 e8 fa 3e db f9 48 b8 00 00 00 00 00 fc ff df 48 8d bb c8 00 00 00 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 e2 04 00 00 48 8b 9b c8 00 00 00 48 b8 00 00 00 RSP: 0018:ffffc90003ef7818 EFLAGS: 00010202 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8797fd9d RDX: 0000000000000019 RSI: ffffffff8797fde6 RDI: 00000000000000c8 RBP: ffff888099848040 R08: ffff88809a5f6440 R09: fffffbfff1860b4c R10: ffffffff8c305a5f R11: fffffbfff1860b4b R12: ffff88809984857e R13: 0000000000000000 R14: ffff888086aa4000 R15: 0000000000000000 FS: 00000000009b4880(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000020000140 CR3: 00000000a7fdf000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: tipc_sendstream+0x4c/0x70 net/tipc/socket.c:1533 sock_sendmsg_nosec net/socket.c:652 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:672 ____sys_sendmsg+0x32f/0x810 net/socket.c:2352 ___sys_sendmsg+0x100/0x170 net/socket.c:2406 __sys_sendmmsg+0x195/0x480 net/socket.c:2496 __do_sys_sendmmsg net/socket.c:2525 [inline] __se_sys_sendmmsg net/socket.c:2522 [inline] __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2522 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x440199 ...
This bug was bisected to commit 0a3e060f340d ("tipc: add test for Nagle algorithm effectiveness"). However, it is not the case, the trouble was from the base in the case of zero data length message sending, we would unexpectedly make an empty 'txq' queue after the 'tipc_msg_append()' in Nagle mode.
A similar crash can be generated even without the bisected patch but at the link layer when it accesses the empty queue.
We solve the issues by building at least one buffer to go with socket's header and an optional data section that may be empty like what we had with the 'tipc_msg_build()'.
Note: the previous commit 4c21daae3dbc ("tipc: Fix NULL pointer dereference in __tipc_sendstream()") is obsoleted by this one since the 'txq' will be never empty and the check of 'skb != NULL' is unnecessary but it is safe anyway.
Reported-by: syzbot+8eac6d030e7807c21d32@syzkaller.appspotmail.com Fixes: c0bceb97db9e ("tipc: add smart nagle feature") Acked-by: Jon Maloy jmaloy@redhat.com Signed-off-by: Tuong Lien tuong.t.lien@dektech.com.au Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/tipc/msg.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/net/tipc/msg.c +++ b/net/tipc/msg.c @@ -221,7 +221,7 @@ int tipc_msg_append(struct tipc_msg *_hd accounted = skb ? msg_blocks(buf_msg(skb)) : 0; total = accounted;
- while (rem) { + do { if (!skb || skb->len >= mss) { prev = skb; skb = tipc_buf_acquire(mss, GFP_KERNEL); @@ -249,7 +249,7 @@ int tipc_msg_append(struct tipc_msg *_hd skb_put(skb, cpy); rem -= cpy; total += msg_blocks(hdr) - curr; - } + } while (rem); return total - accounted; }