padata: Fix possible divide-by-0 panic in padata_mt_helper()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: padata: Fix possible divide-by-0 panic in padata_mt_helper() We are hit with a not easily reproducible divide-by-0 panic in padata.c at bootup time. [ 10.017908] Oops: divide error: 0000 1 PREEMPT SMP NOPTI [ 10.017908] CPU: 26 PID: 2627 Comm: kworker/u1666:1 Not tainted 6.10.0-15.el10.x86_64 #1 [ 10.017908] Hardware name: Lenovo ThinkSystem SR950 [7X12CTO1WW]/[7X12CTO1WW], BIOS [PSE140J-2.30] 07/20/2021 [ 10.017908] Workqueue: events_unbound padata_mt_helper [ 10.017908] RIP: 0010:padata_mt_helper+0x39/0xb0 : [ 10.017963] Call Trace: [ 10.017968] <TASK> [ 10.018004] ? padata_mt_helper+0x39/0xb0 [ 10.018084] process_one_work+0x174/0x330 [ 10.018093] worker_thread+0x266/0x3a0 [ 10.018111] kthread+0xcf/0x100 [ 10.018124] ret_from_fork+0x31/0x50 [ 10.018138] ret_from_fork_asm+0x1a/0x30 [ 10.018147] </TASK> Looking at the padata_mt_helper() function, the only way a divide-by-0 panic can happen is when ps->chunk_size is 0. The way that chunk_size is initialized in padata_do_multithreaded(), chunk_size can be 0 when the min_chunk in the passed-in padata_mt_job structure is 0. Fix this divide-by-0 panic by making sure that chunk_size will be at least 1 no matter what the input parameters are.

References

• https://git.kernel.org/stable/c/ab8b397d5997d8c37610252528edc54bebf9f6d3
• https://git.kernel.org/stable/c/8f5ffd2af7274853ff91d6cd62541191d9fbd10d
• https://git.kernel.org/stable/c/a29cfcb848c31f22b4de6a531c3e1d68c9bfe09f
• https://git.kernel.org/stable/c/924f788c906dccaca30acab86c7124371e1d6f2c
• https://git.kernel.org/stable/c/da0ffe84fcc1627a7dff82c80b823b94236af905
• https://git.kernel.org/stable/c/6d45e1c948a8b7ed6ceddb14319af69424db730c