ghsa-phh3-rpf3-3q9p
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
btrfs: avoid NULL pointer dereference if no valid extent tree
[BUG] Syzbot reported a crash with the following call trace:
BTRFS info (device loop0): scrub: started on devid 1 BUG: kernel NULL pointer dereference, address: 0000000000000208 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 106e70067 P4D 106e70067 PUD 107143067 PMD 0 Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 1 UID: 0 PID: 689 Comm: repro Kdump: loaded Tainted: G O 6.13.0-rc4-custom+ #206 Tainted: [O]=OOT_MODULE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022 RIP: 0010:find_first_extent_item+0x26/0x1f0 [btrfs] Call Trace: scrub_find_fill_first_stripe+0x13d/0x3b0 [btrfs] scrub_simple_mirror+0x175/0x260 [btrfs] scrub_stripe+0x5d4/0x6c0 [btrfs] scrub_chunk+0xbb/0x170 [btrfs] scrub_enumerate_chunks+0x2f4/0x5f0 [btrfs] btrfs_scrub_dev+0x240/0x600 [btrfs] btrfs_ioctl+0x1dc8/0x2fa0 [btrfs] ? do_sys_openat2+0xa5/0xf0 __x64_sys_ioctl+0x97/0xc0 do_syscall_64+0x4f/0x120 entry_SYSCALL_64_after_hwframe+0x76/0x7e
[CAUSE] The reproducer is using a corrupted image where extent tree root is corrupted, thus forcing to use "rescue=all,ro" mount option to mount the image.
Then it triggered a scrub, but since scrub relies on extent tree to find where the data/metadata extents are, scrub_find_fill_first_stripe() relies on an non-empty extent root.
But unfortunately scrub_find_fill_first_stripe() doesn't really expect an NULL pointer for extent root, it use extent_root to grab fs_info and triggered a NULL pointer dereference.
[FIX] Add an extra check for a valid extent root at the beginning of scrub_find_fill_first_stripe().
The new error path is introduced by 42437a6386ff ("btrfs: introduce mount option rescue=ignorebadroots"), but that's pretty old, and later commit b979547513ff ("btrfs: scrub: introduce helper to find and fill sector info for a scrub_stripe") changed how we do scrub.
So for kernels older than 6.6, the fix will need manual backport.
{
"affected": [],
"aliases": [
"CVE-2025-21658"
],
"database_specific": {
"cwe_ids": [
"CWE-476"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-01-21T13:15:09Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: avoid NULL pointer dereference if no valid extent tree\n\n[BUG]\nSyzbot reported a crash with the following call trace:\n\n BTRFS info (device loop0): scrub: started on devid 1\n BUG: kernel NULL pointer dereference, address: 0000000000000208\n #PF: supervisor read access in kernel mode\n #PF: error_code(0x0000) - not-present page\n PGD 106e70067 P4D 106e70067 PUD 107143067 PMD 0\n Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI\n CPU: 1 UID: 0 PID: 689 Comm: repro Kdump: loaded Tainted: G O 6.13.0-rc4-custom+ #206\n Tainted: [O]=OOT_MODULE\n Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS unknown 02/02/2022\n RIP: 0010:find_first_extent_item+0x26/0x1f0 [btrfs]\n Call Trace:\n \u003cTASK\u003e\n scrub_find_fill_first_stripe+0x13d/0x3b0 [btrfs]\n scrub_simple_mirror+0x175/0x260 [btrfs]\n scrub_stripe+0x5d4/0x6c0 [btrfs]\n scrub_chunk+0xbb/0x170 [btrfs]\n scrub_enumerate_chunks+0x2f4/0x5f0 [btrfs]\n btrfs_scrub_dev+0x240/0x600 [btrfs]\n btrfs_ioctl+0x1dc8/0x2fa0 [btrfs]\n ? do_sys_openat2+0xa5/0xf0\n __x64_sys_ioctl+0x97/0xc0\n do_syscall_64+0x4f/0x120\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n \u003c/TASK\u003e\n\n[CAUSE]\nThe reproducer is using a corrupted image where extent tree root is\ncorrupted, thus forcing to use \"rescue=all,ro\" mount option to mount the\nimage.\n\nThen it triggered a scrub, but since scrub relies on extent tree to find\nwhere the data/metadata extents are, scrub_find_fill_first_stripe()\nrelies on an non-empty extent root.\n\nBut unfortunately scrub_find_fill_first_stripe() doesn\u0027t really expect\nan NULL pointer for extent root, it use extent_root to grab fs_info and\ntriggered a NULL pointer dereference.\n\n[FIX]\nAdd an extra check for a valid extent root at the beginning of\nscrub_find_fill_first_stripe().\n\nThe new error path is introduced by 42437a6386ff (\"btrfs: introduce\nmount option rescue=ignorebadroots\"), but that\u0027s pretty old, and later\ncommit b979547513ff (\"btrfs: scrub: introduce helper to find and fill\nsector info for a scrub_stripe\") changed how we do scrub.\n\nSo for kernels older than 6.6, the fix will need manual backport.",
"id": "GHSA-phh3-rpf3-3q9p",
"modified": "2025-01-23T00:33:59Z",
"published": "2025-01-21T15:31:03Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21658"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/24b85a8b0310e0144da9ab30be42e87e6476638a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6aecd91a5c5b68939cf4169e32bc49f3cd2dd329"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/aee5f69f3e6cd82bfefaca1b70b40b6cd8f3f784"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"type": "CVSS_V3"
}
]
}
Sightings
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