CVE-2025-38382 (GCVE-0-2025-38382)
Vulnerability from cvelistv5
Published
2025-07-25 12:53
Modified
2026-08-05 12:01
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix iteration of extrefs during log replay At __inode_add_ref() when processing extrefs, if we jump into the next label we have an undefined value of victim_name.len, since we haven't initialized it before we did the goto. This results in an invalid memory access in the next iteration of the loop since victim_name.len was not initialized to the length of the name of the current extref. Fix this by initializing victim_name.len with the current extref's name length.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1cf474cd474bc5d3ef63086ffd009a87a5b7bb2e
Version: e43eec81c5167b655b72c781b0e75e62a05e415e
Version: e43eec81c5167b655b72c781b0e75e62a05e415e
Version: e43eec81c5167b655b72c781b0e75e62a05e415e
Version: e43eec81c5167b655b72c781b0e75e62a05e415e
Version: 6.1.57   ≤
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix iteration of extrefs during log replay\n\nAt __inode_add_ref() when processing extrefs, if we jump into the next\nlabel we have an undefined value of victim_name.len, since we haven\u0027t\ninitialized it before we did the goto. This results in an invalid memory\naccess in the next iteration of the loop since victim_name.len was not\ninitialized to the length of the name of the current extref.\n\nFix this by initializing victim_name.len with the current extref\u0027s name\nlength."
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              "value": "AV:L - The vulnerable code is only reached through tree-log replay during `mount(2)` of a btrfs volume (open_ctree \u2192 btrfs_replay_log \u2192 __add_inode_ref), so the attacker needs local access to present the crafted image via a block device, loop file, or removable media. There is no network-facing path into btrfs log replay.\nAC:L - Triggering is fully deterministic \u2014 the tree-checker\u0027s `check_inode_extref()` never validates the embedded `parent_objectid` against the item\u0027s hash key, so the attacker simply places a mismatching-parent extref first in the item and sets `super_log_root` so replay runs automatically. No race, timing window, or unpredictable memory layout is involved in reaching the invalid access.\nPR:L - btrfs does not set `FS_USERNS_MOUNT`, but an unprivileged session user routinely causes attacker-supplied btrfs media to be mounted by udisks2/systemd automounters on desktops, kiosks, and shared workstations, and image-processing services loop-mount untrusted images on behalf of low-privileged callers. No elevated capability of the attacker\u0027s own is needed in that scenario.\nUI:N - Once the crafted volume is attached, the automounter mounts it and log replay runs unconditionally because `btrfs_super_log_root(disk_super) != 0` is checked with no operator prompt. The attacker performs the mount-triggering action themselves; no separate victim action is required.\nS:U - The out-of-bounds access and the resulting corruption stay within the kernel\u0027s own security authority. No hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - The uninitialized `victim_name.len` makes `btrfs_get_64()` read past `eb-\u003elen`, and with the accessor\u0027s `ASSERT(check_setget_bounds(...))` compiled out on production kernels, `get_eb_folio_index()` runs off the end of `eb-\u003efolios[]` (index 16 with an attacker-chosen 64K nodesize on 4K pages), turning adjacent slab contents into a `struct folio *` that `folio_address()` dereferences \u2014 an unbounded wild kernel read, not a few-byte bounded one.\nI:H - The out-of-bounds and uninitialized data is interpreted as inode backref metadata and then acted upon: `read_one_inode()` on a garbage `parent_objectid`, `inc_nlink()` on the inode, and `unlink_inode_for_log_replay()` removing directory entries, so kernel memory read out of bounds directly drives modification of filesystem state. Combined with the wild-pointer arithmetic on `eb-\u003efolios[]`, this is memory corruption that must be treated as leverageable for control-flow influence.\nA:H - In the common configurations the bogus folio index yields a NULL or wild `folio_address()` dereference during mount, producing a kernel oops, and with `CONFIG_BTRFS_ASSERT=y` the bounds assertion calls `BUG()` outright. Either outcome is a kernel crash in the mount path."
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    "cveId": "CVE-2025-38382",
    "datePublished": "2025-07-25T12:53:23.665Z",
    "dateReserved": "2025-04-16T04:51:24.010Z",
    "dateUpdated": "2026-08-05T12:01:29.887Z",
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