Btrfs: fix null pointer dereference on compressed write path error
authorFilipe Manana <fdmanana@suse.com>
Fri, 12 Oct 2018 23:37:25 +0000 (00:37 +0100)
committerDavid Sterba <dsterba@suse.com>
Wed, 17 Oct 2018 15:42:46 +0000 (17:42 +0200)
commit3527a018c00e5dbada2f9d7ed5576437b6dd5cfb
tree03ba27ac5ed2e2aa7d70c10b8bf9f2a9cfe18867
parentd9352794dad9f28535439d85a815978878c141ab
Btrfs: fix null pointer dereference on compressed write path error

At inode.c:compress_file_range(), under the "free_pages_out" label, we can
end up dereferencing the "pages" pointer when it has a NULL value. This
case happens when "start" has a value of 0 and we fail to allocate memory
for the "pages" pointer. When that happens we jump to the "cont" label and
then enter the "if (start == 0)" branch where we immediately call the
cow_file_range_inline() function. If that function returns 0 (success
creating an inline extent) or an error (like -ENOMEM for example) we jump
to the "free_pages_out" label and then access "pages[i]" leading to a NULL
pointer dereference, since "nr_pages" has a value greater than zero at
that point.

Fix this by setting "nr_pages" to 0 when we fail to allocate memory for
the "pages" pointer.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201119
Fixes: 771ed689d2cd ("Btrfs: Optimize compressed writeback and reads")
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Liu Bo <bo.liu@linux.alibaba.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fs/btrfs/inode.c