Description
In the Linux kernel, the following vulnerability has been resolved: erofs: handle overlapped pclusters out of crafted images properly syzbot reported a task hang issue due to a deadlock case where it is waiting for the folio lock of a cached folio that will be used for cache I/Os. After looking into the crafted fuzzed image, I found it's formed with several overlapped big pclusters as below: Ext: logical offset | length : physical offset | length 0: 0.. 16384 | 16384 : 151552.. 167936 | 16384 1: 16384.. 32768 | 16384 : 155648.. 172032 | 16384 2: 32768.. 49152 | 16384 : 537223168.. 537239552 | 16384 ... Here, extent 0/1 are physically overlapped although it's entirely _impossible_ for normal filesystem images generated by mkfs. First, managed folios containing compressed data will be marked as up-to-date and then unlocked immediately (unlike in-place folios) when compressed I/Os are complete. If physical blocks are not submitted in the incremental order, there should be separate BIOs to avoid dependency issues. However, the current code mis-arranges z_erofs_fill_bio_vec() and BIO submission which causes unexpected BIO waits. Second, managed folios will be connected to their own pclusters for efficient inter-queries. However, this is somewhat hard to implement easily if overlapped big pclusters exist. Again, these only appear in fuzzed images so let's simply fall back to temporary short-lived pages for correctness. Additionally, it justifies that referenced managed folios cannot be truncated for now and reverts part of commit 2080ca1ed3e4 ("erofs: tidy up `struct z_erofs_bvec`") for simplicity although it shouldn't be any difference.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
8e6c8fa9f2e95c88a642521a5da19a8e31748846 to < c1172e65aad4b115392ea4c6e61e56e5b9b69df4affected8e6c8fa9f2e95c88a642521a5da19a8e31748846 to < 1bf7e414cac303c9aec1be67872e19be8b64980caffected8e6c8fa9f2e95c88a642521a5da19a8e31748846 to < b9b30af0e86ffb485301ecd83b9129c9dfb7ebf8affected8e6c8fa9f2e95c88a642521a5da19a8e31748846 to < 9cfa199bcbbbba31cbf97b2786f44f4464f3f29aaffected8e6c8fa9f2e95c88a642521a5da19a8e31748846 to < 9e2f9d34dd12e6e5b244ec488bcebd0c2d566c50affected
Linux Linux
Default version status: affected
5.13affected0 to < 5.13unaffected6.1.168 to ≤ 6.1.*unaffected6.6.72 to ≤ 6.6.*unaffected6.10.13 to ≤ 6.10.*unaffected6.11.2 to ≤ 6.11.*unaffected6.12 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/c1172e65aad4b115392ea4c6e61e56e5b9b69df4 ↗
- https://git.kernel.org/stable/c/1bf7e414cac303c9aec1be67872e19be8b64980c ↗
- https://git.kernel.org/stable/c/b9b30af0e86ffb485301ecd83b9129c9dfb7ebf8 ↗
- https://git.kernel.org/stable/c/9cfa199bcbbbba31cbf97b2786f44f4464f3f29a ↗
- https://git.kernel.org/stable/c/9e2f9d34dd12e6e5b244ec488bcebd0c2d566c50 ↗
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html ↗
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html ↗
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html ↗