CVE-2025-68821
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2026-01-13

Last updated on: 2026-01-19

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: fuse: fix readahead reclaim deadlock Commit e26ee4efbc79 ("fuse: allocate ff->release_args only if release is needed") skips allocating ff->release_args if the server does not implement open. However in doing so, fuse_prepare_release() now skips grabbing the reference on the inode, which makes it possible for an inode to be evicted from the dcache while there are inflight readahead requests. This causes a deadlock if the server triggers reclaim while servicing the readahead request and reclaim attempts to evict the inode of the file being read ahead. Since the folio is locked during readahead, when reclaim evicts the fuse inode and fuse_evict_inode() attempts to remove all folios associated with the inode from the page cache (truncate_inode_pages_range()), reclaim will block forever waiting for the lock since readahead cannot relinquish the lock because it is itself blocked in reclaim: >>> stack_trace(1504735) folio_wait_bit_common (mm/filemap.c:1308:4) folio_lock (./include/linux/pagemap.h:1052:3) truncate_inode_pages_range (mm/truncate.c:336:10) fuse_evict_inode (fs/fuse/inode.c:161:2) evict (fs/inode.c:704:3) dentry_unlink_inode (fs/dcache.c:412:3) __dentry_kill (fs/dcache.c:615:3) shrink_kill (fs/dcache.c:1060:12) shrink_dentry_list (fs/dcache.c:1087:3) prune_dcache_sb (fs/dcache.c:1168:2) super_cache_scan (fs/super.c:221:10) do_shrink_slab (mm/shrinker.c:435:9) shrink_slab (mm/shrinker.c:626:10) shrink_node (mm/vmscan.c:5951:2) shrink_zones (mm/vmscan.c:6195:3) do_try_to_free_pages (mm/vmscan.c:6257:3) do_swap_page (mm/memory.c:4136:11) handle_pte_fault (mm/memory.c:5562:10) handle_mm_fault (mm/memory.c:5870:9) do_user_addr_fault (arch/x86/mm/fault.c:1338:10) handle_page_fault (arch/x86/mm/fault.c:1481:3) exc_page_fault (arch/x86/mm/fault.c:1539:2) asm_exc_page_fault+0x22/0x27 Fix this deadlock by allocating ff->release_args and grabbing the reference on the inode when preparing the file for release even if the server does not implement open. The inode reference will be dropped when the last reference on the fuse file is dropped (see fuse_file_put() -> fuse_release_end()).
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Meta Information
Published
2026-01-13
Last Modified
2026-01-19
Generated
2026-05-07
AI Q&A
2026-01-14
EPSS Evaluated
2026-05-05
NVD
CVE-2025-68821
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
linux_kernel fuse *
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
What immediate steps should I take to mitigate this vulnerability?

To mitigate this vulnerability, update the Linux kernel to a version that includes the fix for the fuse readahead reclaim deadlock. The fix involves allocating ff->release_args and grabbing the reference on the inode when preparing the file for release, even if the server does not implement open. Applying the patch or upgrading to a kernel version containing commit e26ee4efbc79 will resolve the deadlock issue.


Can you explain this vulnerability to me?

This vulnerability is a deadlock issue in the Linux kernel's fuse filesystem. It occurs because the kernel skips allocating certain release arguments and does not grab a reference on the inode when the server does not implement open. This can lead to an inode being evicted from the dcache while there are ongoing readahead requests. When the server triggers reclaim during these requests, it causes a deadlock because the reclaim process waits for a lock held by the readahead, which itself is blocked by reclaim. The fix involves always allocating release arguments and grabbing the inode reference when preparing the file for release, preventing the deadlock.


How can this vulnerability impact me? :

This vulnerability can cause a deadlock in the Linux kernel's fuse filesystem, potentially leading to system hangs or unresponsiveness when accessing files via fuse. This can disrupt normal file operations and degrade system stability or availability.


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