fix(vfs): saturate EROFS inode/dir/data offset arithmetic#137
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Sibling sweep to the blkszbits shift fix. EROFS computes image byte offsets from parsed nid / inode.size / raw_blkaddr / caller offset without bounding the arithmetic; crafted values overflow usize/u64 (overflow-checks ON = ring-0 panic) before the following bounds check can reject them: - nid_to_offset: meta_blkaddr*block_size + nid*32 (nid is a parsed u64). - read_inode: off + 2 / off + format.size() bounds checks. - readdir: dir_start + dir_size (dir_size = parsed inode.size). - read_flat_plain: raw_blkaddr*block_size + offset, + to_copy. - read_flat_inline: inode_off + format.size(), raw_blkaddr*block_size + blk*block_size + blk_off, inline_start + tail_off, + to_copy. Use saturating_mul/saturating_add so an out-of-range value saturates to a huge offset that the existing '> self.data.len()' checks reject with IoError instead of panicking. Valid images are unaffected.
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Sibling sweep to the blkszbits shift fix (#136). EROFS computes image byte offsets from parsed
nid/inode.size/raw_blkaddr/ calleroffsetwithout bounding the arithmetic; crafted values overflow usize/u64 (overflow-checks ON = ring-0 panic) before the following> self.data.len()bounds check can reject them:nid_to_offset:meta_blkaddr*block_size + nid*32(nid is a parsed u64 →nid*32overflows).read_inode:off + 2/off + format.size().readdir:dir_start + dir_size(dir_size = parsed inode.size).read_flat_plain:raw_blkaddr*block_size + offset,+ to_copy.read_flat_inline:inode_off + format.size(),raw_blkaddr*block_size + blk*block_size + blk_off,inline_start + tail_off,+ to_copy.Use saturating_mul/saturating_add so out-of-range values saturate to a huge offset the existing bounds checks reject with IoError. Valid images unaffected. (readdir name_start slice + the block-relative subtractions verified already-guarded; not changed.) Found via kimi agentic lane + verified/sibling-swept by hand.