From: Sudip Mukherjee <sudipm.mukher...@gmail.com>

commit db973a7289dad24e6c017dcedc6aee886579dc3a upstream.

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.ruff...@canonical.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukher...@gmail.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Cc: Paul Wise <pa...@bonedaddy.net>
Cc: Alexander Viro <v...@zeniv.linux.org.uk>
Cc: Neil Horman <nhor...@tuxdriver.com>
Cc: <sta...@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200416194612.21418-1-sudipm.mukher...@gmail.com
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

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

--- a/fs/coredump.c
+++ b/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


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