mtd: block2mtd: Fix divide error when erase_size is zero

Overview

In the Linux kernel, the following vulnerability has been resolved:

mtd: block2mtd: Fix divide error when erase_size is zero

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.

Affected

• Linux >= ea6d833a3fddcd1d60414d48f34c7f4fbe88608f < 826170a49ca1315af6b293a02200585b1e2186d9
• Linux >= ea6d833a3fddcd1d60414d48f34c7f4fbe88608f < a991c28066e7ba4da7450bb04478849f7ac6a14a
• Linux >= ea6d833a3fddcd1d60414d48f34c7f4fbe88608f < 21d0f05989bf0d5cef57b467a7fa4feefbd7236a
• Linux >= ea6d833a3fddcd1d60414d48f34c7f4fbe88608f < b5965c4221165045e19736794ca5f48ae3d67142
• Linux 3.15

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.