CVE-2022-50286

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

ext4: fix delayed allocation bug in ext4_clu_mapped for bigalloc + inline

When converting files with inline data to extents, delayed allocations made on a file system created with both the bigalloc and inline options can result in invalid extent status cache content, incorrect reserved cluster counts, kernel memory leaks, and potential kernel panics.

With bigalloc, the code that determines whether a block must be delayed allocated searches the extent tree to see if that block maps to a previously allocated cluster. If not, the block is delayed allocated, and otherwise, it isnt. However, if the inline option is also used, and if the file containing the block is marked as able to store data inline, there isnt a valid extent tree associated with the file. The current code in ext4_clu_mapped() calls ext4_find_extent() to search the non-existent tree for a previously allocated cluster anyway, which typically finds nothing, as desired. However, a side effect of the search can be to cache invalid content from the non-existent tree (garbage) in the extent status tree, including bogus entries in the pending reservation tree.

To fix this, avoid searching the extent tree when allocating blocks for bigalloc + inline files that are being converted from inline to extent mapped.

Affected Software

References

• https://git.kernel.org/stable/c/131294c35ed6f777bd4e79d42af13b5c41bf2775
• https://git.kernel.org/stable/c/6f4200ec76a0d31200c308ec5a71c68df5417004
• https://git.kernel.org/stable/c/81b915181c630ee1cffa052e52874fe4e1ba91ac
• https://git.kernel.org/stable/c/9404839e0c9db5a517ea83c0ca3388b39d105fdf
• https://git.kernel.org/stable/c/c0c8edbc8abbe8f16d80a1d794d1ba2c12b6f193
• https://git.kernel.org/stable/c/d440d6427a5e3a877c1c259b8d2b216ddb65e185