CVE-2024-35807

NameCVE-2024-35807
DescriptionIn the Linux kernel, the following vulnerability has been resolved: ext4: fix corruption during on-line resize We observed a corruption during on-line resize of a file system that is larger than 16 TiB with 4k block size. With having more then 2^32 blocks resize_inode is turned off by default by mke2fs. The issue can be reproduced on a smaller file system for convenience by explicitly turning off resize_inode. An on-line resize across an 8 GiB boundary (the size of a meta block group in this setup) then leads to a corruption: dev=/dev/<some_dev> # should be >= 16 GiB mkdir -p /corruption /sbin/mke2fs -t ext4 -b 4096 -O ^resize_inode $dev $((2 * 2**21 - 2**15)) mount -t ext4 $dev /corruption dd if=/dev/zero bs=4096 of=/corruption/test count=$((2*2**21 - 4*2**15)) sha1sum /corruption/test # 79d2658b39dcfd77274e435b0934028adafaab11 /corruption/test /sbin/resize2fs $dev $((2*2**21)) # drop page cache to force reload the block from disk echo 1 > /proc/sys/vm/drop_caches sha1sum /corruption/test # 3c2abc63cbf1a94c9e6977e0fbd72cd832c4d5c3 /corruption/test 2^21 = 2^15*2^6 equals 8 GiB whereof 2^15 is the number of blocks per block group and 2^6 are the number of block groups that make a meta block group. The last checksum might be different depending on how the file is laid out across the physical blocks. The actual corruption occurs at physical block 63*2^15 = 2064384 which would be the location of the backup of the meta block group's block descriptor. During the on-line resize the file system will be converted to meta_bg starting at s_first_meta_bg which is 2 in the example - meaning all block groups after 16 GiB. However, in ext4_flex_group_add we might add block groups that are not part of the first meta block group yet. In the reproducer we achieved this by substracting the size of a whole block group from the point where the meta block group would start. This must be considered when updating the backup block group descriptors to follow the non-meta_bg layout. The fix is to add a test whether the group to add is already part of the meta block group or not.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
ReferencesDLA-3840-1, DLA-3842-1, ELA-1116-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
linux (PTS)jessie, jessie (lts)3.16.84-1vulnerable
stretch (security)4.9.320-2vulnerable
stretch (lts), stretch4.9.320-3vulnerable
buster (security), buster, buster (lts)4.19.316-1fixed
bullseye5.10.223-1fixed
bullseye (security)5.10.226-1fixed
bookworm6.1.106-3fixed
bookworm (security)6.1.112-1fixed
sid, trixie6.11.5-1fixed
linux-4.19 (PTS)jessie, jessie (lts)4.19.316-1~deb8u1fixed
stretch (security)4.19.232-1~deb9u1vulnerable
stretch (lts), stretch4.19.316-1~deb9u1fixed
linux-5.10 (PTS)buster, buster (lts)5.10.226-1~deb10u1fixed
buster (security)5.10.218-1~deb10u1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
linuxsourcejessie(unfixed)end-of-life
linuxsourcestretch(unfixed)end-of-life
linuxsourcebuster4.19.316-1DLA-3840-1
linuxsourcebullseye5.10.216-1
linuxsourcebookworm6.1.85-1
linuxsource(unstable)6.7.12-1
linux-4.19sourcejessie4.19.316-1~deb8u1ELA-1116-1
linux-4.19sourcestretch4.19.316-1~deb9u1ELA-1116-1
linux-5.10sourcebuster5.10.216-1~deb10u1DLA-3842-1

Notes

https://git.kernel.org/linus/a6b3bfe176e8a5b05ec4447404e412c2a3fc92cc (6.9-rc1)

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