CVE-2026-100073

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

ext4: fix transaction overflow during writeback

Commit 95ad8ee45cdb ("ext4: correct the reserved credits for extent

conversion") was correct to note that we need to reserve enough credits

for all extents possibly underlying a large folio. However it was too

eager to reduce the number of reserved credits. Extent conversion may

not only need to touch several leaf extent blocks, it may also need to

split extents - for example a single large unwritten extent may need to

be split into many small written ones in case of sparse folio dirtying.

This can thus result not only in extent leaf modifications but also in a

need to allocate new extent tree nodes. As a result the reserved

transaction credits were not sufficient in some corner cases. Use

ext4_meta_trans_blocks() for correct upper bound credit estimate.