CVE-2022-49706 zonefs: fix zonefs_iomap_begin() for reads
A local attacker can trigger a kernel warning and infinite loop in the zonefs filesystem by reading a sequential zone file at a specific offset, causing a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2022-49706?
CVE-2022-49706 is a high-severity denial of service vulnerability in Linux kernel, published on 26 Feb 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
zonefs: fix zonefs_iomap_begin() for reads
If a readahead is issued to a sequential zone file with an offset exactly equal to the current file size, the iomap type is set to IOMAP_UNWRITTEN, which will prevent an IO, but the iomap length is calculated as 0. This causes a WARN_ON() in iomap_iter():
[17309.548939] WARNING: CPU: 3 PID: 2137 at fs/iomap/iter.c:34 iomap_iter+0x9cf/0xe80 [...] [17309.650907] RIP: 0010:iomap_iter+0x9cf/0xe80 [...] [17309.754560] Call Trace: [17309.757078] <TASK> [17309.759240] ? lock_is_held_type+0xd8/0x130 [17309.763531] iomap_readahead+0x1a8/0x870 [17309.767550] ? iomap_read_folio+0x4c0/0x4c0 [17309.771817] ? lockdep_hardirqs_on_prepare+0x400/0x400 [17309.778848] ? lock_release+0x370/0x750 [17309.784462] ? folio_add_lru+0x217/0x3f0 [17309.790220] ? reacquire_held_locks+0x4e0/0x4e0 [17309.796543] read_pages+0x17d/0xb60 [17309.801854] ? folio_add_lru+0x238/0x3f0 [17309.807573] ? readahead_expand+0x5f0/0x5f0 [17309.813554] ? policy_node+0xb5/0x140 [17309.819018] page_cache_ra_unbounded+0x27d/0x450 [17309.825439] filemap_get_pages+0x500/0x1450 [17309.831444] ? filemap_add_folio+0x140/0x140 [17309.837519] ? lock_is_held_type+0xd8/0x130 [17309.843509] filemap_read+0x28c/0x9f0 [17309.848953] ? zonefs_file_read_iter+0x1ea/0x4d0 [zonefs] [17309.856162] ? trace_contention_end+0xd6/0x130 [17309.862416] ? __mutex_lock+0x221/0x1480 [17309.868151] ? zonefs_file_read_iter+0x166/0x4d0 [zonefs] [17309.875364] ? filemap_get_pages+0x1450/0x1450 [17309.881647] ? __mutex_unlock_slowpath+0x15e/0x620 [17309.888248] ? wait_for_completion_io_timeout+0x20/0x20 [17309.895231] ? lock_is_held_type+0xd8/0x130 [17309.901115] ? lock_is_held_type+0xd8/0x130 [17309.906934] zonefs_file_read_iter+0x356/0x4d0 [zonefs] [17309.913750] new_sync_read+0x2d8/0x520 [17309.919035] ? __x64_sys_lseek+0x1d0/0x1d0
Furthermore, this causes iomap_readahead() to loop forever as iomap_readahead_iter() always returns 0, making no progress.
Fix this by treating reads after the file size as access to holes, setting the iomap type to IOMAP_HOLE, the iomap addr to IOMAP_NULL_ADDR and using the length argument as is for the iomap length. To simplify the code with this change, zonefs_iomap_begin() is split into the read variant, zonefs_read_iomap_begin() and zonefs_read_iomap_ops, and the write variant, zonefs_write_iomap_begin() and zonefs_write_iomap_ops.
Weakness: CWE-125
Which versions are affected by CVE-2022-49706?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2022-49706?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2022-49706 being exploited?
There is no known exploitation of CVE-2022-49706 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2022-49706, GHSA-fv86-c5hh-rvpj, UBUNTU-CVE-2022-49706.