CVE-2022-49464

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

erofs: fix buffer copy overflow of ztailpacking feature

I got some KASAN report as below:

[ 46.959738] ================================================================== [ 46.960430] BUG: KASAN: use-after-free in z_erofs_shifted_transform+0x2bd/0x370 [ 46.960430] Read of size 4074 at addr ffff8880300c2f8e by task fssum/188 ... [ 46.960430] Call Trace: [ 46.960430] <TASK> [ 46.960430] dump_stack_lvl+0x41/0x5e [ 46.960430] print_report.cold+0xb2/0x6b7 [ 46.960430] ? z_erofs_shifted_transform+0x2bd/0x370 [ 46.960430] kasan_report+0x8a/0x140 [ 46.960430] ? z_erofs_shifted_transform+0x2bd/0x370 [ 46.960430] kasan_check_range+0x14d/0x1d0 [ 46.960430] memcpy+0x20/0x60 [ 46.960430] z_erofs_shifted_transform+0x2bd/0x370 [ 46.960430] z_erofs_decompress_pcluster+0xaae/0x1080

The root cause is that the tail pcluster won't be a complete filesystem block anymore. So if ztailpacking is used, the second part of an uncompressed tail pcluster may not be rq->pageofs_out.

This vulnerability is rated as Important because successful exploitation could result in kernel memory corruption and potential local privilege escalation if an attacker can mount a specially crafted EROFS image. Under standard Red Hat Enterprise Linux deployments, non-privileged users cannot mount arbitrary filesystem media without elevated privileges. Furthermore, Red Hat Enterprise Linux kernels do not backport the upstream code introducing the ztailpacking feature flaw, leaving supported Red Hat products unaffected.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.