From: Weijie Yang <[email protected]> Subject: zram: avoid kunmap_atomic() of a NULL pointer
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 <[email protected]> Cc: Sergey Senozhatsky <[email protected]> Cc: Dan Streetman <[email protected]> Cc: Nitin Gupta <[email protected]> Cc: Weijie Yang <[email protected]> Acked-by: Jerome Marchand <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> --- drivers/block/zram/zram_drv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff -puN drivers/block/zram/zram_drv.c~zram-avoid-kunmap_atomic-a-null-pointer drivers/block/zram/zram_drv.c --- a/drivers/block/zram/zram_drv.c~zram-avoid-kunmap_atomic-a-null-pointer +++ a/drivers/block/zram/zram_drv.c @@ -560,7 +560,8 @@ static int zram_bvec_write(struct zram * } if (page_zero_filled(uncmem)) { - kunmap_atomic(user_mem); + if (user_mem) + kunmap_atomic(user_mem); /* Free memory associated with this sector now. */ bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value); zram_free_page(zram, index); _ -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
