CVE-2025-21896

01/Description

In the Linux kernel, the following vulnerability has been resolved: fuse: revert back to __readahead_folio() for readahead In commit 3eab9d7bc2f4 ("fuse: convert readahead to use folios"), the logic was converted to using the new folio readahead code, which drops the reference on the folio once it is locked, using an inferred reference on the folio. Previously we held a reference on the folio for the entire duration of the readpages call. This is fine, however for the case for splice pipe responses where we will remove the old folio and splice in the new folio (see fuse_try_move_page()), we assume that there is a reference held on the folio for ap->folios, which is no longer the case. To fix this, revert back to __readahead_folio() which allows us to hold the reference on the folio for the duration of readpages until either we drop the reference ourselves in fuse_readpages_end() or the reference is dropped after it's replaced in the page cache in the splice case. This will fix the UAF bug that was reported.

02/Affected products

linux: linux kernel

03/References2

• git.kernel.org/stable/c/0c67c37e1710b2a8f61c8a02db95a51fe577e2c1 Patch
• git.kernel.org/stable/c/60db11f1b7fba4a66b117ea998d965818784a98d Patch