From db973a7289dad24e6c017dcedc6aee886579dc3a Mon Sep 17 00:00:00 2001
From: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Date: Mon, 20 Apr 2020 18:14:20 -0700
Subject: [PATCH] coredump: fix null pointer dereference on coredump
Git-commit: db973a7289dad24e6c017dcedc6aee886579dc3a
Patch-mainline: v5.7-rc3
References: git-fixes

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:

    RIP: 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:

    format_corename failed
    Aborting core

Fixes: 315c69261dd3 ("coredump: split pipe command whitespace before expanding template")
Reported-by: Matthew Ruffell <matthew.ruffell@canonical.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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>
Link: http://lkml.kernel.org/r/20200416194612.21418-1-sudipm.mukherjee@gmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

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

diff --git a/fs/coredump.c b/fs/coredump.c
index f8296a82d01d..408418e6aa13 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -211,6 +211,8 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm,
 			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
-- 
2.16.4