seq_file: disallow extremely large seq buffer allocations

commit 8cae8cd89f05f6de223d63e6d15e31c8ba9cf53b upstream.

There is no reasonable need for a buffer larger than this, and it avoids
int overflow pitfalls.

Fixes: 058504edd026 ("fs/seq_file: fallback to vmalloc allocation")
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Reported-by: Qualys Security Advisory <qsa@qualys.com>
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/seq_file.c b/fs/seq_file.c
index cb11a34fb8714d6f9f6804fc9c62a376edac6e12..1cfae052439d9a220a053fcfa0cf47f01f439968 100644 (file)
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -32,6 +32,9 @@ static void seq_set_overflow(struct seq_file *m)
 
 static void *seq_buf_alloc(unsigned long size)
 {
+       if (unlikely(size > MAX_RW_COUNT))
+               return NULL;
+
        return kvmalloc(size, GFP_KERNEL_ACCOUNT);
 }