[PATCH 1/1] swapfile: swap_info_get: Check for swap_info[type] == NULL

From: Kautuk Consul
Date: Mon Dec 26 2011 - 06:51:31 EST

From: Kautuk Consul <consul.kautuk@xxxxxxxxx>

If the swapfile type encoded within entry.val is corrupted in
such a way that the swap_info[type] == NULL, then the code in
swap_info_get will cause a NULL pointer exception.

Assuming that the code in swap_info_get attempts to validate the
swapfile type by checking its range, another bad_nofile check would
be to check for check whether the swap_info[type] pointer is NULL.

Adding a NULL check for swap_info[type] to be reagrded as a "bad_nofile"
error scenario.

Signed-off-by: Kautuk Consul <consul.kautuk@xxxxxxxxx>
mm/swapfile.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index b1cd120..7bdbe91 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -483,6 +483,8 @@ static struct swap_info_struct *swap_info_get(swp_entry_t entry)
if (type >= nr_swapfiles)
goto bad_nofile;
p = swap_info[type];
+ if (!p)
+ goto bad_nofile;
if (!(p->flags & SWP_USED))
goto bad_device;
offset = swp_offset(entry);

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