CVE-2025-40006
- Published: 2025-10-20T16:15:37.240
- Last modified: 1761075085
In the Linux kernel, the following vulnerability has been resolved:
mm/hugetlb: fix folio is still mapped when deleted
Migration may be raced with fallocating hole. remove_inode_single_folio
will unmap the folio if the folio is still mapped. However, it’s called
without folio lock. If the folio is migrated and the mapped pte has been
converted to migration entry, folio_mapped() returns false, and won’t
unmap it. Due to extra refcount held by remove_inode_single_folio,
migration fails, restores migration entry to normal pte, and the folio is
mapped again. As a result, we triggered BUG in filemap_unaccount_folio.
The log is as follows:
BUG: Bad page cache in process hugetlb pfn:156c00
page: refcount:515 mapcount:0 mapping:0000000099fef6e1 index:0x0 pfn:0x156c00
head: order:9 mapcount:1 entire_mapcount:1 nr_pages_mapped:0 pincount:0
aops:hugetlbfs_aops ino:dcc dentry name(?):”my_hugepage_file”
flags: 0x17ffffc00000c1(locked|waiters|head|node=0|zone=2|lastcpupid=0x1fffff)
page_type: f4(hugetlb)
page dumped because: still mapped when deleted
CPU: 1 UID: 0 PID: 395 Comm: hugetlb Not tainted 6.17.0-rc5-00044-g7aac71907bde-dirty #484 NONE
Hardware name: QEMU Ubuntu 24.04 PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
Call Trace:
dump_stack_lvl+0x4f/0x70
filemap_unaccount_folio+0xc4/0x1c0
__filemap_remove_folio+0x38/0x1c0
filemap_remove_folio+0x41/0xd0
remove_inode_hugepages+0x142/0x250
hugetlbfs_fallocate+0x471/0x5a0
vfs_fallocate+0x149/0x380
Hold folio lock before checking if the folio is mapped to avold race with
migration.
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How to fix CVE-2025-40006
Description: In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: fix folio is still mapped when deleted Migration may be raced with fallocating hole. remove_inode_single_folio will unmap the folio if the folio is still mapped. However, it’s called without folio lock. If the folio is migrated and the mapped pte has been converted to […]
Exploit Difficulty: HARD
⏱️ Time to exploit: > 4 hours
🛠️ Required skills: Advanced security expertise
💰 Public exploits: Rare or not public
How to Fix:
- Check if you're running the affected product
- Update to the latest patched version
- If patching is not immediately possible: restrict network exposure, apply least-privilege access
- Test the fix in a staging environment first
- Review logs for signs of exploitation
- Monitor for IOCs (Indicators of Compromise)
- Enable automatic security updates
- Set up vulnerability monitoring
- Review and harden security configurations
Exploit Difficulty Assessment
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