From: Pei Xiao <xiaopei01@kylinos.cn> stable inclusion from stable-v6.6.160 commit bff83b723e93acc788bd690dc4bc1f6f4356c35b category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/20696 CVE: CVE-2026-98722 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit b5965c4221165045e19736794ca5f48ae3d67142 ] The erase size is parsed from the "block2mtd" module parameter and can be set to zero. add_device() then evaluates if (size % erase_size) with a zero divisor, which triggers a divide error: divide error: 0000 [#1] PREEMPT SMP PTI RIP: 0010:add_device drivers/mtd/devices/block2mtd.c:296 [inline] RIP: 0010:block2mtd_setup2+0x592/0xda0 drivers/mtd/devices/block2mtd.c:459 Call Trace: block2mtd_setup+0x27/0xe0 drivers/mtd/devices/block2mtd.c:476 param_attr_store+0x214/0x310 kernel/params.c:589 module_attr_store+0x65/0x90 kernel/params.c:904 kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345 ... Reject a zero erase size before performing the modulo operation so the existing "erasesize must be a divisor of device size" error path reports the invalid argument and frees the device. Fixes: ea6d833a3fdd ("mtd: block2mtd: check device size") Reported-by: syzbot+b320a4d5f65a61dbbf89@syzkaller.appspotmail.com Closes: https://lore.kernel.org/lkml/6a7b58ba.ac361c09.22ff0a.0045.GAE@google.com/ Suggested-by: Jörn Engel <joern@barelysecure.org> Cc: stable@vger.kernel.org Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Yi Yang <yiyang13@huawei.com> --- drivers/mtd/devices/block2mtd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/mtd/devices/block2mtd.c b/drivers/mtd/devices/block2mtd.c index 502c30124aa6..1eb6bcab7adc 100644 --- a/drivers/mtd/devices/block2mtd.c +++ b/drivers/mtd/devices/block2mtd.c @@ -297,7 +297,7 @@ static struct block2mtd_dev *add_device(char *devname, int erase_size, } size = bdev_nr_bytes(bdev); - if ((long)size % erase_size) { + if (!erase_size || (long)size % erase_size) { pr_err("erasesize must be a divisor of device size\n"); goto err_free_block2mtd; } -- 2.25.1