fcntl(0, F_SETOWN, 0x80000000) triggers: UBSAN: Undefined behaviour in fs/fcntl.c:118:7 negation of -2147483648 cannot be represented in type 'int': CPU: 1 PID: 18261 Comm: syz-executor Not tainted 4.8.1-0-syzkaller #1 ... Call Trace: ... [<ffffffffad8f0868>] ? f_setown+0x1d8/0x200 [<ffffffffad8f19a9>] ? SyS_fcntl+0x999/0xf30 [<ffffffffaed1fb00>] ? entry_SYSCALL_64_fastpath+0x23/0xc1
Fix that by checking the arg parameter properly (against INT_MAX) and return immediatelly in case it is wrong. No error is returned, the same as in other cases. Signed-off-by: Jiri Slaby <jsl...@suse.cz> Cc: Jeff Layton <jlay...@poochiereds.net> Cc: "J. Bruce Fields" <bfie...@fieldses.org> Cc: Alexander Viro <v...@zeniv.linux.org.uk> Cc: linux-fsde...@vger.kernel.org --- fs/fcntl.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/fcntl.c b/fs/fcntl.c index 350a2c8cfd28..bfc3b040d956 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -112,6 +112,10 @@ void f_setown(struct file *filp, unsigned long arg, int force) enum pid_type type; struct pid *pid; int who = arg; + + if (arg > INT_MAX) + return; + type = PIDTYPE_PID; if (who < 0) { type = PIDTYPE_PGID; -- 2.10.1