CVE-2025-38691
pNFS: Fix uninited ptr deref in block/scsi layout
Description
In the Linux kernel, the following vulnerability has been resolved: pNFS: Fix uninited ptr deref in block/scsi layout The error occurs on the third attempt to encode extents. When function ext_tree_prepare_commit() reallocates a larger buffer to retry encoding extents, the "layoutupdate_pages" page array is initialized only after the retry loop. But ext_tree_free_commitdata() is called on every iteration and tries to put pages in the array, thus dereferencing uninitialized pointers. An additional problem is that there is no limit on the maximum possible buffer_size. When there are too many extents, the client may create a layoutcommit that is larger than the maximum possible RPC size accepted by the server. During testing, we observed two typical scenarios. First, one memory page for extents is enough when we work with small files, append data to the end of the file, or preallocate extents before writing. But when we fill a new large file without preallocating, the number of extents can be huge, and counting the number of written extents in ext_tree_encode_commit() does not help much. Since this number increases even more between unlocking and locking of ext_tree, the reallocated buffer may not be large enough again and again.
INFO
Published Date :
Sept. 4, 2025, 4:15 p.m.
Last Modified :
Sept. 5, 2025, 5:47 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Apply the Linux kernel update.
- Verify pNFS component configurations.
- Test file operations thoroughly.
- Monitor system stability.
References to Advisories, Solutions, and Tools
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CVE-2025-38691.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-38691 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
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stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-38691
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Sep. 04, 2025
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: pNFS: Fix uninited ptr deref in block/scsi layout The error occurs on the third attempt to encode extents. When function ext_tree_prepare_commit() reallocates a larger buffer to retry encoding extents, the "layoutupdate_pages" page array is initialized only after the retry loop. But ext_tree_free_commitdata() is called on every iteration and tries to put pages in the array, thus dereferencing uninitialized pointers. An additional problem is that there is no limit on the maximum possible buffer_size. When there are too many extents, the client may create a layoutcommit that is larger than the maximum possible RPC size accepted by the server. During testing, we observed two typical scenarios. First, one memory page for extents is enough when we work with small files, append data to the end of the file, or preallocate extents before writing. But when we fill a new large file without preallocating, the number of extents can be huge, and counting the number of written extents in ext_tree_encode_commit() does not help much. Since this number increases even more between unlocking and locking of ext_tree, the reallocated buffer may not be large enough again and again. Added Reference https://git.kernel.org/stable/c/24334f3cf8a294f253071b5bf22d754dbb6d0f2d Added Reference https://git.kernel.org/stable/c/2896f101110076ac6bf99d7aaf463d61e26f89dd Added Reference https://git.kernel.org/stable/c/37c3443a2685528f972d910a6fb87716b96fef46 Added Reference https://git.kernel.org/stable/c/4f783333cbfa2ee7d4aa8e47f6bd1b3f77534fcf Added Reference https://git.kernel.org/stable/c/579b85f893d9885162e1cabf99a4a088916e143e Added Reference https://git.kernel.org/stable/c/94ec6d939031a616474376dadbf4a8d0ef8b0bcc Added Reference https://git.kernel.org/stable/c/9768797c219326699778fba9cd3b607b2f1e7950 Added Reference https://git.kernel.org/stable/c/9be5c04beca3202d0a5f09fb4b2ecb644caa0bc5 Added Reference https://git.kernel.org/stable/c/f0b2eee3fbba9b7e3746ef698424ef5e4a197776