ghsa-36gh-mcf5-3vpm
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
btrfs: scrub: handle RST lookup error correctly
[BUG] When running btrfs/060 with forced RST feature, it would crash the following ASSERT() inside scrub_read_endio():
ASSERT(sector_nr < stripe->nr_sectors);
Before that, we would have tree dump from btrfs_get_raid_extent_offset(), as we failed to find the RST entry for the range.
[CAUSE] Inside scrub_submit_extent_sector_read() every time we allocated a new bbio we immediately called btrfs_map_block() to make sure there was some RST range covering the scrub target.
But if btrfs_map_block() fails, we immediately call endio for the bbio, while the bbio is newly allocated, it's completely empty.
Then inside scrub_read_endio(), we go through the bvecs to find the sector number (as bi_sector is no longer reliable if the bio is submitted to lower layers).
And since the bio is empty, such bvecs iteration would not find any sector matching the sector, and return sector_nr == stripe->nr_sectors, triggering the ASSERT().
[FIX] Instead of calling btrfs_map_block() after allocating a new bbio, call btrfs_map_block() first.
Since our only objective of calling btrfs_map_block() is only to update stripe_len, there is really no need to do that after btrfs_alloc_bio().
This new timing would avoid the problem of handling empty bbio completely, and in fact fixes a possible race window for the old code, where if the submission thread is the only owner of the pending_io, the scrub would never finish (since we didn't decrease the pending_io counter).
Although the root cause of RST lookup failure still needs to be addressed.
{
"affected": [],
"aliases": [
"CVE-2024-41067"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-07-29T15:15:14Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: scrub: handle RST lookup error correctly\n\n[BUG]\nWhen running btrfs/060 with forced RST feature, it would crash the\nfollowing ASSERT() inside scrub_read_endio():\n\n\tASSERT(sector_nr \u003c stripe-\u003enr_sectors);\n\nBefore that, we would have tree dump from\nbtrfs_get_raid_extent_offset(), as we failed to find the RST entry for\nthe range.\n\n[CAUSE]\nInside scrub_submit_extent_sector_read() every time we allocated a new\nbbio we immediately called btrfs_map_block() to make sure there was some\nRST range covering the scrub target.\n\nBut if btrfs_map_block() fails, we immediately call endio for the bbio,\nwhile the bbio is newly allocated, it\u0027s completely empty.\n\nThen inside scrub_read_endio(), we go through the bvecs to find\nthe sector number (as bi_sector is no longer reliable if the bio is\nsubmitted to lower layers).\n\nAnd since the bio is empty, such bvecs iteration would not find any\nsector matching the sector, and return sector_nr == stripe-\u003enr_sectors,\ntriggering the ASSERT().\n\n[FIX]\nInstead of calling btrfs_map_block() after allocating a new bbio, call\nbtrfs_map_block() first.\n\nSince our only objective of calling btrfs_map_block() is only to update\nstripe_len, there is really no need to do that after btrfs_alloc_bio().\n\nThis new timing would avoid the problem of handling empty bbio\ncompletely, and in fact fixes a possible race window for the old code,\nwhere if the submission thread is the only owner of the pending_io, the\nscrub would never finish (since we didn\u0027t decrease the pending_io\ncounter).\n\nAlthough the root cause of RST lookup failure still needs to be\naddressed.",
"id": "GHSA-36gh-mcf5-3vpm",
"modified": "2024-07-29T15:30:45Z",
"published": "2024-07-29T15:30:44Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-41067"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/17d1fd302a53d7e456a7412da74be74a0cf63a72"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2c49908634a2b97b1c3abe0589be2739ac5e7fd5"
}
],
"schema_version": "1.4.0",
"severity": []
}
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