Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: mm/ptdump: always stabilise against page table freeing using init_mm Previous commits have established the invariant that kernel page table freeing is performed while an mmap read lock on init_mm is held, which fixes races between ptdump and kernel page table freeing over init_mm. However, x86 and arm64 can perform a ptdump over an mm other than init_mm via ptdump_walk_pgd() and since kernel memory ranges are shared across non-kernel mm's, this means that the race still exists for these cases. Fix this by acquiring a nested mmap write lock for init_mm in ptdump_walk_pgd(). This is safe as we take this after mmap write locking the mm, and nothing acquires the init_mm lock first before locking an arbitrary mm, so no deadlock is possible. Also update walk_page_range_debug() to assert that init_mm is write locked, add a comment explaining why and remove some redundant code, and eliminate the unnecessary and confusing invocation of walk_kernel_page_table_range(). We can safely remove the non-NULL check for walk.mm, as the mmap lock asserts would NULL pointer deref if it was (and of course no callers do this). The first point at which ptdump can race kernel page table freeing is commit b6bdb7517c3d ("mm/vmalloc: add interfaces to free unmapped page table"), so we target this in the Fixes tag.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e before 3c0391b9a774cc0854f3152e484a9d4835b12b40; affected b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e before cbd9583bb6f70733d0022a66d3546a15c76ae744; affected b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e before 76df4edf7d61ecb711bc517ff4c20a5e85c4e9f7; affected b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e before b9c6d048bdfaae78d7d921b454f7de7baefaa2f0; affected b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e before 7f740664aec1f832953c2e6d9b8920cd6c8bcc0c; affected b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e before 4adc4c9a9a43d61fe476dfe10811f3df2e7e4106; affected b6bdb7517c3d3f41f20e5c2948d6bc3f8897394e before 27c32e5538344b13c1505a08861e04620c125d47; affected 31895cfd79564111cdd5a9f48c5d491ae26a238e; affected 9c7f7bdb1932f8c1e5f80d32c717184701afe701; affected acdb4981644c8e31ccee294bdefff475c0cf587b; affected 0454e2fad9306961540ee7e84da47a8e345b7d22; affected 4.4.125 before 4.5; affected 4.9.91 before 4.10; affected 4.14.31 before 4.15; affected 4.15.14 before 4.16 |
| Linux / Linux | affected 4.16; unaffected 0 before 4.16; unaffected 5.10.266 through 5.10.*; unaffected 5.15.217 through 5.15.*; unaffected 6.6.153 through 6.6.*; unaffected 6.12.105 through 6.12.*; unaffected 6.18.45 through 6.18.*; unaffected 7.1.9 through 7.1.*; unaffected 7.2 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/3c0391b9a774cc0854f3152e484a9d4835b12b40
- https://git.kernel.org/stable/c/cbd9583bb6f70733d0022a66d3546a15c76ae744
- https://git.kernel.org/stable/c/76df4edf7d61ecb711bc517ff4c20a5e85c4e9f7
- https://git.kernel.org/stable/c/b9c6d048bdfaae78d7d921b454f7de7baefaa2f0
- https://git.kernel.org/stable/c/7f740664aec1f832953c2e6d9b8920cd6c8bcc0c
- https://git.kernel.org/stable/c/4adc4c9a9a43d61fe476dfe10811f3df2e7e4106
- https://git.kernel.org/stable/c/27c32e5538344b13c1505a08861e04620c125d47