CVE-2024-35807

Description

In 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.

Gravité et risque d'exploitation

CVE-2024-35807 obtient un score CVSS de 0.0/10, soit une gravité non évaluée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.27 %, ce qui la place devant 18.1 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions 6.9, <=6.1.*, <a6b3bfe176e8a5b05ec4447404e412c2a3fc92cc, <e8e8b197317228b5089ed9e7802dadf3ccaa027a, 0, <75cc31c2e7193b69f5d25650bda5bb42ed92f8a1, <b461910af8ba3bed80f48c2bf852686d05c6fc5c, <722d2c01b8b108f8283d1b7222209d5b2a5aa7bd, 5.15.154, 6.8.3, <=5.10.*, <=6.6.*, 5.10.215, <=5.4.*, 4.19.312, <=4.19.*, <239c669edb2bffa1aa2612519b1d438ab35d6be6, 5.4.274, <=6.8.*, <3.7, 6.7.12, <=*, 3.7, <=5.15.*, <=6.7.*, <ee4e9c1976147a850f6085a13fca95bcaa00d84c, 01f795f9e0d67adeccc61a8b20c28acb45fa5fd8, <fb1088d51bbaa0faec5a55d4f5818a9ab79e24df, <37b6a3ba793bbbae057f5b991970ebcc52cb3db5, 6.1.84, 6.6.24) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/75cc31c2e7193b69f5d25650bda5bb42ed92f8a1
• https://git.kernel.org/stable/c/ee4e9c1976147a850f6085a13fca95bcaa00d84c
• https://git.kernel.org/stable/c/e8e8b197317228b5089ed9e7802dadf3ccaa027a
• https://git.kernel.org/stable/c/239c669edb2bffa1aa2612519b1d438ab35d6be6
• https://git.kernel.org/stable/c/fb1088d51bbaa0faec5a55d4f5818a9ab79e24df
• https://git.kernel.org/stable/c/37b6a3ba793bbbae057f5b991970ebcc52cb3db5
• https://git.kernel.org/stable/c/b461910af8ba3bed80f48c2bf852686d05c6fc5c
• https://git.kernel.org/stable/c/722d2c01b8b108f8283d1b7222209d5b2a5aa7bd
• https://git.kernel.org/stable/c/a6b3bfe176e8a5b05ec4447404e412c2a3fc92cc