lib/iov_iter: fix to increase non slab folio refcount

published 2025-05-01 18 mo ago modified 2026-08-05 3 mo ago also EUVD-2025-13036

cvss: 7.8; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 6%
public exploits: 0; none known

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

When testing EROFS file-backed mount over v9fs on qemu, I encountered a folio UAF issue. The page sanity check reports the following call trace. The root cause is that pages in bvec are coalesced across a folio bounary. The refcount of all non-slab folios should be increased to ensure p9_releas_pages can put them correctly.

BUG: Bad page state in process md5sum pfn:18300 page: refcount:0 mapcount:0 mapping:00000000d5ad8e4e index:0x60 pfn:0x18300 head: order:0 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 aops:z_erofs_aops ino:30b0f dentry name(?):"GoogleExtServicesCn.apk" flags: 0x100000000000041(locked|head|node=0|zone=1) raw: 0100000000000041 dead000000000100 dead000000000122 ffff888014b13bd0 raw: 0000000000000060 0000000000000020 00000000ffffffff 0000000000000000 head: 0100000000000041 dead000000000100 dead000000000122 ffff888014b13bd0 head: 0000000000000060 0000000000000020 00000000ffffffff 0000000000000000 head: 0100000000000000 0000000000000000 ffffffffffffffff 0000000000000000 head: 0000000000000010 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set Call Trace: dump_stack_lvl+0x53/0x70 bad_page+0xd4/0x220 __free_pages_ok+0x76d/0xf30 __folio_put+0x230/0x320 p9_release_pages+0x179/0x1f0 p9_virtio_zc_request+0xa2a/0x1230 p9_client_zc_rpc.constprop.0+0x247/0x700 p9_client_read_once+0x34d/0x810 p9_client_read+0xf3/0x150 v9fs_issue_read+0x111/0x360 netfs_unbuffered_read_iter_locked+0x927/0x1390 netfs_unbuffered_read_iter+0xa2/0xe0 vfs_iocb_iter_read+0x2c7/0x460 erofs_fileio_rq_submit+0x46b/0x5b0 z_erofs_runqueue+0x1203/0x21e0 z_erofs_readahead+0x579/0x8b0 read_pages+0x19f/0xa70 page_cache_ra_order+0x4ad/0xb80 filemap_readahead.isra.0+0xe7/0x150 filemap_get_pages+0x7aa/0x1890 filemap_read+0x320/0xc80 vfs_read+0x6c6/0xa30 ksys_read+0xf9/0x1c0 do_syscall_64+0x9e/0x1a0 entry_SYSCALL_64_after_hwframe+0x71/0x79

Patch / fix

fixed in 1 links 2

Linux Linux 6.14.4, 6.15

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-37779 updated 2026-11-07

kernel: lib/iov_iter: fix to increase non slab folio refcount

Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 6% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.8	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD	3.1	5.5	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

Linux Linux

Classification

Weakness

CWE-415 Double Free

Technology feeds

Linux kernel rss critical rss

References

Sources

CVE List CVE-2025-37779
NVD CVE-2025-37779

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary