kernel/signal.c: avoid undefined behaviour in kill_something_info

commit 4ea7701 upstream.

When running kill(72057458746458112, 0) in userspace I hit the following
issue.

  UBSAN: Undefined behaviour in kernel/signal.c:1462:11
  negation of -2147483648 cannot be represented in type 'int':
  CPU: 226 PID: 9849 Comm: test Tainted: G    B          ---- -------   3.10.0-327.53.58.70.x86_64_ubsan+ torvalds#116
  Hardware name: Huawei Technologies Co., Ltd. RH8100 V3/BC61PBIA, BIOS BLHSV028 11/11/2014
  Call Trace:
    dump_stack+0x19/0x1b
    ubsan_epilogue+0xd/0x50
    __ubsan_handle_negate_overflow+0x109/0x14e
    SYSC_kill+0x43e/0x4d0
    SyS_kill+0xe/0x10
    system_call_fastpath+0x16/0x1b

Add code to avoid the UBSAN detection.

[[email protected]: tweak comment]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: zhongjiang <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Xishi Qiu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Cc: Guenter Roeck <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: xiongzhongjiang

kernel/signal.c

@@ -1392,6 +1392,10 @@ static int kill_something_info(int sig, struct siginfo *info, pid_t pid)
 		return ret;
 	}
 
+	/* -INT_MIN is undefined.  Exclude this case to avoid a UBSAN warning */
+	if (pid == INT_MIN)
+		return -ESRCH;
+
 	read_lock(&tasklist_lock);
 	if (pid != -1) {
 		ret = __kill_pgrp_info(sig, info,