From 340eb9b208105e5c86b936d7f8b8d8e865f1bc6f Mon Sep 17 00:00:00 2001 From: Weijie Yang Date: Thu, 13 Nov 2014 15:19:05 -0800 Subject: [PATCH] zram: avoid kunmap_atomic() of a NULL pointer commit c406515239376fc93a30d5d03192182160cbd3fb upstream. zram could kunmap_atomic() a NULL pointer in a rare situation: a zram page becomes a full-zeroed page after a partial write io. The current code doesn't handle this case and performs kunmap_atomic() on a NULL pointer, which panics the kernel. This patch fixes this issue. Signed-off-by: Weijie Yang Cc: Sergey Senozhatsky Cc: Dan Streetman Cc: Nitin Gupta Cc: Weijie Yang Acked-by: Jerome Marchand Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- drivers/block/zram/zram_drv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 51c557c..d8ddb8e 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -447,7 +447,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, } if (page_zero_filled(uncmem)) { - kunmap_atomic(user_mem); + if (user_mem) + kunmap_atomic(user_mem); /* Free memory associated with this sector now. */ write_lock(&zram->meta->tb_lock); zram_free_page(zram, index); -- 2.7.4