Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:[EOL][EOL]ext4: fix deadlock due to mbcache entry corruption[EOL][EOL]When manipulating xattr blocks, we can deadlock infinitely looping[EOL]inside ext4_xattr_block_set() where we constantly keep finding xattr[EOL]block for reuse in mbcache but we are unable to reuse it because its[EOL]reference count is too big. This happens because cache entry for the[EOL]xattr block is marked as reusable (e_reusable set) although its[EOL]reference count is too big. When this inconsistency happens, this[EOL]inconsistent state is kept indefinitely and so ext4_xattr_block_set()[EOL]keeps retrying indefinitely.[EOL][EOL]The inconsistent state is caused by non-atomic update of e_reusable bit.[EOL]e_reusable is part of a bitfield and e_reusable update can race with[EOL]update of e_referenced bit in the same bitfield resulting in loss of one[EOL]of the updates. Fix the problem by using atomic bitops instead.[EOL][EOL]This bug has been around for many years, but it became *much* easier[EOL]to hit after commit 65f8b80053a1 ("ext4: fix race when reusing xattr[EOL]blocks").