Fix a use after free bug in kernel->userspace relay file support
Coverity spotted what looks like a real possible case of using a variable
after it has been freed. The problem is in
kernel/relay.c::relay_open_buf()
If the code hits "goto free_buf;" it ends up in this code :
free_buf:
relay_destroy_buf(buf); <--- calls kfree() on 'buf'.
free_name:
kfree(tmpname);
end:
return buf; <-- use after free of 'buf'.
I read through the callers and they all handle a NULL return from this
function as an error (and hitting the 'free_buf' label only happens on
failure to chan->cb->create_buf_file(), so that looks like a clear error to
me).
The patch simply sets 'buf' to NULL after the call to
relay_destroy_buf(buf); - as far as I can see that should take care of the
problem.
The patch also corrects a reference to a documentation file while
I was at it.
Note from Mathieu: the documentation reference change should have been
done in a separate patch, but I guess no one will really care.
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Acked-by: "David J. Wilder" <wilder@us.ibm.com>
Tested-by: "David J. Wilder" <wilder@us.ibm.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Tom Zanussi <zanussi@us.ibm.com>
Cc: Karim Yaghmour <karim@opersys.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/relay.c b/kernel/relay.c
index 510fbbd..ad85501 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -1,7 +1,7 @@
/*
* Public API and common code for kernel->userspace relay file support.
*
- * See Documentation/filesystems/relayfs.txt for an overview of relayfs.
+ * See Documentation/filesystems/relay.txt for an overview.
*
* Copyright (C) 2002-2005 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
* Copyright (C) 1999-2005 - Karim Yaghmour (karim@opersys.com)
@@ -426,6 +426,7 @@
free_buf:
relay_destroy_buf(buf);
+ buf = NULL;
free_name:
kfree(tmpname);
end:
