GHSA-2CVC-2CMJ-7863
Vulnerability from github – Published: 2024-10-21 12:30 – Updated: 2024-10-24 15:31In the Linux kernel, the following vulnerability has been resolved:
f2fs: check discard support for conventional zones
As the helper function f2fs_bdev_support_discard() shows, f2fs checks if the target block devices support discard by calling bdev_max_discard_sectors() and bdev_is_zoned(). This check works well for most cases, but it does not work for conventional zones on zoned block devices. F2fs assumes that zoned block devices support discard, and calls __submit_discard_cmd(). When __submit_discard_cmd() is called for sequential write required zones, it works fine since __submit_discard_cmd() issues zone reset commands instead of discard commands. However, when __submit_discard_cmd() is called for conventional zones, __blkdev_issue_discard() is called even when the devices do not support discard.
The inappropriate __blkdev_issue_discard() call was not a problem before the commit 30f1e7241422 ("block: move discard checks into the ioctl handler") because __blkdev_issue_discard() checked if the target devices support discard or not. If not, it returned EOPNOTSUPP. After the commit, __blkdev_issue_discard() no longer checks it. It always returns zero and sets NULL to the given bio pointer. This NULL pointer triggers f2fs_bug_on() in __submit_discard_cmd(). The BUG is recreated with the commands below at the umount step, where /dev/nullb0 is a zoned null_blk with 5GB total size, 128MB zone size and 10 conventional zones.
$ mkfs.f2fs -f -m /dev/nullb0 $ mount /dev/nullb0 /mnt $ for ((i=0;i<5;i++)); do dd if=/dev/zero of=/mnt/test bs=65536 count=1600 conv=fsync; done $ umount /mnt
To fix the BUG, avoid the inappropriate __blkdev_issue_discard() call. When discard is requested for conventional zones, check if the device supports discard or not. If not, return EOPNOTSUPP.
{
"affected": [],
"aliases": [
"CVE-2024-47680"
],
"database_specific": {
"cwe_ids": [
"CWE-476"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-10-21T12:15:05Z",
"severity": "MODERATE"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: check discard support for conventional zones\n\nAs the helper function f2fs_bdev_support_discard() shows, f2fs checks if\nthe target block devices support discard by calling\nbdev_max_discard_sectors() and bdev_is_zoned(). This check works well\nfor most cases, but it does not work for conventional zones on zoned\nblock devices. F2fs assumes that zoned block devices support discard,\nand calls __submit_discard_cmd(). When __submit_discard_cmd() is called\nfor sequential write required zones, it works fine since\n__submit_discard_cmd() issues zone reset commands instead of discard\ncommands. However, when __submit_discard_cmd() is called for\nconventional zones, __blkdev_issue_discard() is called even when the\ndevices do not support discard.\n\nThe inappropriate __blkdev_issue_discard() call was not a problem before\nthe commit 30f1e7241422 (\"block: move discard checks into the ioctl\nhandler\") because __blkdev_issue_discard() checked if the target devices\nsupport discard or not. If not, it returned EOPNOTSUPP. After the\ncommit, __blkdev_issue_discard() no longer checks it. It always returns\nzero and sets NULL to the given bio pointer. This NULL pointer triggers\nf2fs_bug_on() in __submit_discard_cmd(). The BUG is recreated with the\ncommands below at the umount step, where /dev/nullb0 is a zoned null_blk\nwith 5GB total size, 128MB zone size and 10 conventional zones.\n\n$ mkfs.f2fs -f -m /dev/nullb0\n$ mount /dev/nullb0 /mnt\n$ for ((i=0;i\u003c5;i++)); do dd if=/dev/zero of=/mnt/test bs=65536 count=1600 conv=fsync; done\n$ umount /mnt\n\nTo fix the BUG, avoid the inappropriate __blkdev_issue_discard() call.\nWhen discard is requested for conventional zones, check if the device\nsupports discard or not. If not, return EOPNOTSUPP.",
"id": "GHSA-2cvc-2cmj-7863",
"modified": "2024-10-24T15:31:07Z",
"published": "2024-10-21T12:30:54Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-47680"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/43aec4d01bd2ce961817a777b3846f8318f398e4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7bd7ce68ddad5a28565e42ef21cacaff113773a9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d2352b57897f6a3349666fc318dcbec99092c6a5"
}
],
"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"
}
]
}
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