Description
In the Linux kernel, the following vulnerability has been resolved: cifs: Release folio lock on fscache read hit. Under the current code, when cifs_readpage_worker is called, the call contract is that the callee should unlock the page. This is documented in the read_folio section of Documentation/filesystems/vfs.rst as: > The filesystem should unlock the folio once the read has completed, > whether it was successful or not. Without this change, when fscache is in use and cache hit occurs during a read, the page lock is leaked, producing the following stack on subsequent reads (via mmap) to the page: $ cat /proc/3890/task/12864/stack [<0>] folio_wait_bit_common+0x124/0x350 [<0>] filemap_read_folio+0xad/0xf0 [<0>] filemap_fault+0x8b1/0xab0 [<0>] __do_fault+0x39/0x150 [<0>] do_fault+0x25c/0x3e0 [<0>] __handle_mm_fault+0x6ca/0xc70 [<0>] handle_mm_fault+0xe9/0x350 [<0>] do_user_addr_fault+0x225/0x6c0 [<0>] exc_page_fault+0x84/0x1b0 [<0>] asm_exc_page_fault+0x27/0x30 This requires a reboot to resolve; it is a deadlock. Note however that the call to cifs_readpage_from_fscache does mark the page clean, but does not free the folio lock. This happens in __cifs_readpage_from_fscache on success. Releasing the lock at that point however is not appropriate as cifs_readahead also calls cifs_readpage_from_fscache and *does* unconditionally release the lock after its return. This change therefore effectively makes cifs_readpage_worker work like cifs_readahead.
Product status
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before c3ac8323f2f5b50e32681c254b8318f7fa2dc3f4
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 5a87735675147f848445f05fd1f06168188f91af
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 4259dd534245579c966c53c15187cc8e9461d6e9
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 6e74926ede96470be84e66a1c576982fe4f8ea79
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 961f7ce16223aee2db583a43877d84e6d1f2b857
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 9e725386d4262ef23ae51993f04602bc535b5be2
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 7a9fb689c1a1dc373887621a3bfa3810df0abde4
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 before 69513dd669e243928f7450893190915a88f84a2b
4.14.324
4.19.293
5.4.255
5.10.192
5.15.128
6.1.47
6.4.12
6.5
References
git.kernel.org/...c/c3ac8323f2f5b50e32681c254b8318f7fa2dc3f4
git.kernel.org/...c/5a87735675147f848445f05fd1f06168188f91af
git.kernel.org/...c/4259dd534245579c966c53c15187cc8e9461d6e9
git.kernel.org/...c/6e74926ede96470be84e66a1c576982fe4f8ea79
git.kernel.org/...c/961f7ce16223aee2db583a43877d84e6d1f2b857
git.kernel.org/...c/9e725386d4262ef23ae51993f04602bc535b5be2
git.kernel.org/...c/7a9fb689c1a1dc373887621a3bfa3810df0abde4
git.kernel.org/...c/69513dd669e243928f7450893190915a88f84a2b
