Note: Versions mentioned in the description apply only to the upstream kernel-64k-modules-core package and not the kernel-64k-modules-core package as distributed by Centos. See How to fix? for Centos:9 relevant fixed versions and status.

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

netfs: Fix missing xas_retry() calls in xarray iteration

netfslib has a number of places in which it performs iteration of an xarray whilst being under the RCU read lock. It should call xas_retry() as the first thing inside of the loop and do "continue" if it returns true in case the xarray walker passed out a special value indicating that the walk needs to be redone from the root[*].

Fix this by adding the missing retry checks.

[*] I wonder if this should be done inside xas_find(), xas_next_node() and suchlike, but I'm told that's not an simple change to effect.

This can cause an oops like that below. Note the faulting address - this is an internal value (|0x2) returned from xarray.

BUG: kernel NULL pointer dereference, address: 0000000000000402 ... RIP: 0010:netfs_rreq_unlock+0xef/0x380 [netfs] ... Call Trace: netfs_rreq_assess+0xa6/0x240 [netfs] netfs_readpage+0x173/0x3b0 [netfs] ? init_wait_var_entry+0x50/0x50 filemap_read_page+0x33/0xf0 filemap_get_pages+0x2f2/0x3f0 filemap_read+0xaa/0x320 ? do_filp_open+0xb2/0x150 ? rmqueue+0x3be/0xe10 ceph_read_iter+0x1fe/0x680 [ceph] ? new_sync_read+0x115/0x1a0 new_sync_read+0x115/0x1a0 vfs_read+0xf3/0x180 ksys_read+0x5f/0xe0 do_syscall_64+0x38/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae

Changes:

ver #2)

• Changed an unsigned int to a size_t to reduce the likelihood of an overflow as per Willy's suggestion.
• Added an additional patch to fix the maths.

• https://access.redhat.com/security/cve/CVE-2022-49810
• https://git.kernel.org/stable/c/7e043a80b5dae5c2d2cf84031501de7827fd6c00
• https://git.kernel.org/stable/c/b2cc07a76f1eb12de3b22caf5fdbf856a7bef16d