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Tuong Lien authored
syzbot found the following issue: WARNING: CPU: 0 PID: 6808 at include/linux/thread_info.h:150 check_copy_size include/linux/thread_info.h:150 [inline] WARNING: CPU: 0 PID: 6808 at include/linux/thread_info.h:150 copy_from_iter include/linux/uio.h:144 [inline] WARNING: CPU: 0 PID: 6808 at include/linux/thread_info.h:150 tipc_msg_append+0x49a/0x5e0 net/tipc/msg.c:242 Kernel panic - not syncing: panic_on_warn set ... This happens after commit 5e9eeccc ("tipc: fix NULL pointer dereference in streaming") that tried to build at least one buffer even when the message data length is zero... However, it now exposes another bug that the 'mss' can be zero and the 'cpy' will be negative, thus the above kernel WARNING will appear! The zero value of 'mss' is never expected because it means Nagle is not enabled for the socket (actually the socket type was 'SOCK_SEQPACKET'), so the function 'tipc_msg_append()' must not be called at all. But that was in this particular case since the message data length was zero, and the 'send <= maxnagle' check became true. We resolve the issue by explicitly checking if Nagle is enabled for the socket, i.e. 'maxnagle != 0' before calling the 'tipc_msg_append()'. We also reinforce the function to against such a negative values if any. Reported-by: syzbot+75139a7d2605236b0b7f@syzkaller.appspotmail.com Fixes: c0bceb97 ("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>
c9aa81fa