CVE-2021-47004

In the Linux kernel, the following vulnerability has been resolved: f2fs:
fix to avoid touching checkpointed data in get_victim() In CP disabling
mode, there are two issues when using LFS or SSR | AT_SSR mode to select
victim: 1. LFS is set to find source section during GC, the victim should
have no checkpointed data, since after GC, section could not be set free
for reuse. Previously, we only check valid chpt blocks in current segment
rather than section, fix it. 2. SSR | AT_SSR are set to find target segment
for writes which can be fully filled by checkpointed and newly written
blocks, we should never select such segment, otherwise it can cause panic
or data corruption during allocation, potential case is described as below:
a) target segment has ‘n’ (n < 512) ckpt valid blocks b) GC migrates ‘n’
valid blocks to other segment (segment is still in dirty list) c) GC
migrates ‘512 - n’ blocks to target segment (segment has ‘n’ cp_vblocks and
‘512 - n’ vblocks) d) If GC selects target segment via {AT,}SSR allocator,
however there is no free space in targe segment.