Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: NFSD: check truncate permission under inode lock nfsd_setattr() checks whether a size update needs NFSD_MAY_TRUNC before it takes inode_lock(). The comparison uses the file size sampled by that unlocked read, but the actual ATTR_SIZE update is applied later under inode_lock() by notify_change(). This leaves a TOCTOU window for append-only files. If a client sends a SETATTR that does not shrink the file at the time of the unlocked sample, a concurrent append can extend the file before nfsd_setattr() takes inode_lock(). notify_change() then applies a real truncation without the NFSD_MAY_TRUNC check that rejects IS_APPEND(inode). The VFS truncate syscall paths perform their own append-only checks before calling notify_change(), so NFSD must make this decision against the locked size it is about to change. Split the write-count acquisition from the truncation permission check. Keep get_write_access() before the locked setattr work, then recheck whether the requested size is below i_size_read(inode) after inode_lock() has been acquired and before notify_change(ATTR_SIZE). This also avoids the plain unlocked inode->i_size load.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 783112f7401ff449d979530209b3f6c2594fdb4e before 52d0c5bdfe232c9974d4b11f97078b9c7814f05d; affected 783112f7401ff449d979530209b3f6c2594fdb4e before 3afa17d93ba8c925f49370c816c6dae5112d8c24; affected 783112f7401ff449d979530209b3f6c2594fdb4e before d8352da196349182e1afd5a93308256cddc0a97d; affected 783112f7401ff449d979530209b3f6c2594fdb4e before 44086254479035de42ca3d286ecf25521d4e6325; affected 783112f7401ff449d979530209b3f6c2594fdb4e before b778e0e0a16759f22a70579c3cf8d254a40d4a7f; affected 604a3c407026d6162d15300478e63f901e435efc; affected cc4d5dc73841b98d33cdfb9822d70b0aac4beca5; affected 3ee4f442e5b37a537297b812557b1163f96b5399; affected a3c6cbc4eac4473ed5461d5faae2794d3e5c0e44; affected 982898d7f97a35447403c3fcecc0d96c646ce101; affected 3.2.89 before 3.3; affected 3.16.44 before 3.17; affected 4.4.53 before 4.5; affected 4.9.14 before 4.10; affected 4.10.2 before 4.11 |
| Linux / Linux | affected 4.11; unaffected 0 before 4.11; unaffected 6.6.160 through 6.6.*; unaffected 6.12.109 through 6.12.*; unaffected 6.18.50 through 6.18.*; unaffected 7.2.4 through 7.2.*; unaffected 7.3 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/52d0c5bdfe232c9974d4b11f97078b9c7814f05d
- https://git.kernel.org/stable/c/3afa17d93ba8c925f49370c816c6dae5112d8c24
- https://git.kernel.org/stable/c/d8352da196349182e1afd5a93308256cddc0a97d
- https://git.kernel.org/stable/c/44086254479035de42ca3d286ecf25521d4e6325
- https://git.kernel.org/stable/c/b778e0e0a16759f22a70579c3cf8d254a40d4a7f
ADP enrichment
No English description supplied.
No references supplied.