UBUNTU-CVE-2025-40205
In the Linux kernel, the following vulnerability has been resolved: btrfs: avoid potential out-of-bounds in btrfs_encode_fh() The function btrfs_encode_fh() does not properly account for the three cases it handles. Before writing to the file handle (fh), the function only returns to the user BTRFS_FID_SIZE_NON_CONNECTABLE (5 dwords, 20 bytes) or BTRFS_FID_SIZE_CONNECTABLE (8 dwords, 32 bytes). However, when a parent exists and the root ID of the parent and the inode are different, the function writes BTRFS_FID_SIZE_CONNECTABLE_ROOT (10 dwords, 40 bytes). If *max_len is not large enough, this write goes out of bounds because BTRFS_FID_SIZE_CONNECTABLE_ROOT is greater than BTRFS_FID_SIZE_CONNECTABLE originally returned. This results in an 8-byte out-of-bounds write at fid->parent_root_objectid = parent_root_id. A previous attempt to fix this issue was made but was lost. https://lore.kernel.org/all/[email protected]/ Although this issue does not seem to be easily triggerable, it is a potential memory corruption bug that should be fixed. This patch resolves the issue by ensuring the function returns the appropriate size for all three cases and validates that *max_len is large enough before writing any data.
02 / AFFECTED SOFTWARE
Affected packages
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03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: btrfs: avoid potential out-of-bounds in btrfs_encode_fh() The function btrfs_encode_fh() does not properly account for the three cases it handles. Before writing to the file handle (fh), the function only returns to the user BTRFS_FID_SIZE_NON_CONNECTABLE (5 dwords, 20 bytes) or BTRFS_FID_SIZE_CONNECTABLE (8 dwords, 32 bytes). However, when a parent exists and the root ID of the parent and the inode are different, the function writes BTRFS_FID_SIZE_CONNECTABLE_ROOT (10 dwords, 40 bytes). If *max_len is not large enough, this write goes out of bounds because BTRFS_FID_SIZE_CONNECTABLE_ROOT is greater than BTRFS_FID_SIZE_CONNECTABLE originally returned. This results in an 8-byte out-of-bounds write at fid->parent_root_objectid = parent_root_id. A previous attempt to fix this issue was made but was lost. https://lore.kernel.org/all/[email protected]/ Although this issue does not seem to be easily triggerable, it is a potential memory corruption bug that should be fixed. This patch resolves the issue by ensuring the function returns the appropriate size for all three cases and validates that *max_len is large enough before writing any data.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/dff4f9ff5d7f289e4545cc936362e01ed3252742
- https://git.kernel.org/stable/c/0276c8582488022f057b4cec21975a5edf079f47
- https://git.kernel.org/stable/c/361d67276eb8ec6be8f27f4ad6c6090459438fee
- https://git.kernel.org/stable/c/43143776b0a7604d873d1a6f3e552a00aa930224
- https://git.kernel.org/stable/c/60de2f55d2aca53e81b4ef2a67d7cc9e1eb677db
- https://git.kernel.org/stable/c/742b44342204e5dfe3926433823623c1a0c581df
- https://git.kernel.org/stable/c/d3a9a8e1275eb9b87f006b5562a287aea3f6885f
- https://git.kernel.org/stable/c/d91f6626133698362bba08fbc04bd72c466806d3
- https://git.kernel.org/stable/c/dff4f9ff5d7f289e4545cc936362e01ed3252742
- https://ubuntu.com/security/CVE-2025-40205
- https://ubuntu.com/security/notices/USN-8029-1
- https://ubuntu.com/security/notices/USN-8029-2
- https://ubuntu.com/security/notices/USN-8029-3
- https://ubuntu.com/security/notices/USN-8030-1
- https://ubuntu.com/security/notices/USN-8033-1
- https://ubuntu.com/security/notices/USN-8033-2
- https://ubuntu.com/security/notices/USN-8033-3
- https://ubuntu.com/security/notices/USN-8033-4
- https://ubuntu.com/security/notices/USN-8033-5
- https://ubuntu.com/security/notices/USN-8033-6
- https://ubuntu.com/security/notices/USN-8033-7
- https://ubuntu.com/security/notices/USN-8033-8
- https://ubuntu.com/security/notices/USN-8034-1
- https://ubuntu.com/security/notices/USN-8034-2
- https://ubuntu.com/security/notices/USN-8048-1
- https://ubuntu.com/security/notices/USN-8095-1
- https://ubuntu.com/security/notices/USN-8095-2
- https://ubuntu.com/security/notices/USN-8095-3
- https://ubuntu.com/security/notices/USN-8095-4
- https://ubuntu.com/security/notices/USN-8095-5
- https://ubuntu.com/security/notices/USN-8100-1
- https://ubuntu.com/security/notices/USN-8125-1
- https://ubuntu.com/security/notices/USN-8126-1
- https://ubuntu.com/security/notices/USN-8141-1
- https://ubuntu.com/security/notices/USN-8163-1
- https://ubuntu.com/security/notices/USN-8163-2
- https://ubuntu.com/security/notices/USN-8165-1
- https://ubuntu.com/security/notices/USN-8243-1
- https://ubuntu.com/security/notices/USN-8261-1
- https://www.cve.org/CVERecord?id=CVE-2025-40205