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Thu, 13 Aug 2026 10:49:41 +0800 Message-ID: Date: Thu, 13 Aug 2026 10:49:38 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mtd: block2mtd: Fix divide error when erase_size is zero To: linux-kernel@vger.kernel.org References: <25ec7ba58facdf29b42ca43dcf11cd98e2089a5f.1786589041.git.xiaopei01@kylinos.cn> From: Pei Xiao In-Reply-To: <25ec7ba58facdf29b42ca43dcf11cd98e2089a5f.1786589041.git.xiaopei01@kylinos.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 在 2026/8/13 10:48, Pei Xiao 写道: > 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 > Cc: stable@vger.kernel.org > Signed-off-by: Pei Xiao > --- > changes in v3: > 1.remove (long) cast due to build errors in 32bit config systems Add. > 2.changes git log about (long) cast > > changlogs in v2: > 1.Add Suggested-by tag > 2.remove unnecessary (long) cast from the size > --- > 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 03e80b2c4f5a..349fa07be314 100644 > --- a/drivers/mtd/devices/block2mtd.c > +++ b/drivers/mtd/devices/block2mtd.c > @@ -293,7 +293,7 @@ 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; > }