CVE-2021-47636

/// Technical description

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

ubifs: Fix read out-of-bounds in ubifs_wbuf_write_nolock()

Function ubifs_wbuf_write_nolock() may access buf out of bounds in

following process:

ubifs_wbuf_write_nolock():

aligned_len = ALIGN(len, 8); // Assume len = 4089, aligned_len = 4096

if (aligned_len <= wbuf->avail) ... // Not satisfy

if (wbuf->used) {

ubifs_leb_write() // Fill some data in avail wbuf

len -= wbuf->avail; // len is still not 8-bytes aligned

aligned_len -= wbuf->avail;

}

n = aligned_len >> c->max_write_shift;

if (n) {

n <<= c->max_write_shift;

err = ubifs_leb_write(c, wbuf->lnum, buf + written,

wbuf->offs, n);

// n > len, read out of bounds less than 8(n-len) bytes

}

, which can be catched by KASAN:

=========================================================

BUG: KASAN: slab-out-of-bounds in ecc_sw_hamming_calculate+0x1dc/0x7d0

Read of size 4 at addr ffff888105594ff8 by t

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References