CVE-2021-47117

In the Linux kernel, the following vulnerability has been resolved:

ext4: fix bug on in ext4_es_cache_extent as ext4_split_extent_at failed

We got follow bug_on when run fsstress with injecting IO fault: [130747.323114] kernel BUG at fs/ext4/extents_status.c:762! [130747.323117] Internal error: Oops - BUG: 0 [#1] SMP …… [130747.334329] Call trace: [130747.334553] ext4_es_cache_extent+0x150/0x168 [ext4] [130747.334975] ext4_cache_extents+0x64/0xe8 [ext4] [130747.335368] ext4_find_extent+0x300/0x330 [ext4] [130747.335759] ext4_ext_map_blocks+0x74/0x1178 [ext4] [130747.336179] ext4_map_blocks+0x2f4/0x5f0 [ext4] [130747.336567] ext4_mpage_readpages+0x4a8/0x7a8 [ext4] [130747.336995] ext4_readpage+0x54/0x100 [ext4] [130747.337359] generic_file_buffered_read+0x410/0xae8 [130747.337767] generic_file_read_iter+0x114/0x190 [130747.338152] ext4_file_read_iter+0x5c/0x140 [ext4] [130747.338556] __vfs_read+0x11c/0x188 [130747.338851] vfs_read+0x94/0x150 [130747.339110] ksys_read+0x74/0xf0

This patchs modification is according to Jan Karas suggestion in: https://patchwork.ozlabs.org/project/linux-ext4/patch/20210428085158.3728201-1-yebin10@huawei.com/ I see. Now I understand your patch. Honestly, seeing how fragile is trying to fix extent tree after split has failed in the middle, I would probably go even further and make sure we fix the tree properly in case of ENOSPC and EDQUOT (those are easily user triggerable). Anything else indicates a HW problem or fs corruption so Id rather leave the extent tree as is and dont try to fix it (which also means we will not create overlapping extents).

Affected Software

References

• https://git.kernel.org/stable/c/082cd4ec240b8734a82a89ffb890216ac98fec68
• https://git.kernel.org/stable/c/48105dc98c9ca35af418746277b087cb2bc6df7c
• https://git.kernel.org/stable/c/569496aa3776eea1ff0d49d0174ac1b7e861e107
• https://git.kernel.org/stable/c/5b3a9a2be59478b013a430ac57b0f3d65471b071
• https://git.kernel.org/stable/c/920697b004e49cb026e2e15fe91be065bf0741b7
• https://git.kernel.org/stable/c/d3b668b96ad3192c0581a248ae2f596cd054792a
• https://git.kernel.org/stable/c/d8116743ef5432336289256b2f7c117299213eb9
• https://git.kernel.org/stable/c/e33bafad30d34cfa5e9787cb099cab05e2677fcb