[patch 14/15] coredump: fix null pointer dereference on coredump

[Andrew Morton <akpm@linux-foundation.org>]

From: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Subject: coredump: fix null pointer dereference on coredump

If the core_pattern is set to "|" and any process segfaults then we get
a null pointer derefernce while trying to coredump. The call stack shows:
[  108.212680] RIP: 0010:do_coredump+0x628/0x11c0

When the core_pattern has only "|" there is no use of trying the coredump
and we can check that while formating the corename and exit with an error.

After this change I get:
[   48.453756] format_corename failed
[   48.453758] Aborting core

Link: http://lkml.kernel.org/r/20200416194612.21418-1-sudipm.mukherjee@gmail.com
Fixes: 315c69261dd3 ("coredump: split pipe command whitespace before expanding template")
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Reported-by: Matthew Ruffell <matthew.ruffell@canonical.com>
Cc: Paul Wise <pabs3@bonedaddy.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/coredump.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/coredump.c~coredump-fix-null-pointer-dereference-on-coredump
+++ a/fs/coredump.c
@@ -211,6 +211,8 @@ static int format_corename(struct core_n
 			return -ENOMEM;
 		(*argv)[(*argc)++] = 0;
 		++pat_ptr;
+		if (!(*pat_ptr))
+			return -ENOMEM;
 	}
 
 	/* Repeat as long as we have more pattern to process and more output
_