5.4-stable review patch. If anyone has any objections, please let me know.
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From: Kairui Song kasong@tencent.com
commit be48c412f6ebf38849213c19547bc6d5b692b5e5 upstream.
Patch series "zram: fix backing device setup issue", v2.
This series fixes two bugs of backing device setting:
- ZRAM should reject using a zero sized (or the uninitialized ZRAM device itself) as the backing device. - Fix backing device leaking when removing a uninitialized ZRAM device.
This patch (of 2):
Setting a zero sized block device as backing device is pointless, and one can easily create a recursive loop by setting the uninitialized ZRAM device itself as its own backing device by (zram0 is uninitialized):
echo /dev/zram0 > /sys/block/zram0/backing_dev
It's definitely a wrong config, and the module will pin itself, kernel should refuse doing so in the first place.
By refusing to use zero sized device we avoided misuse cases including this one above.
Link: https://lkml.kernel.org/r/20241209165717.94215-1-ryncsn@gmail.com Link: https://lkml.kernel.org/r/20241209165717.94215-2-ryncsn@gmail.com Fixes: 013bf95a83ec ("zram: add interface to specif backing device") Signed-off-by: Kairui Song kasong@tencent.com Reported-by: Desheng Wu deshengwu@tencent.com Reviewed-by: Sergey Senozhatsky senozhatsky@chromium.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/block/zram/zram_drv.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -495,6 +495,12 @@ static ssize_t backing_dev_store(struct }
nr_pages = i_size_read(inode) >> PAGE_SHIFT; + /* Refuse to use zero sized device (also prevents self reference) */ + if (!nr_pages) { + err = -EINVAL; + goto out; + } + bitmap_sz = BITS_TO_LONGS(nr_pages) * sizeof(long); bitmap = kvzalloc(bitmap_sz, GFP_KERNEL); if (!bitmap) {