zram: fix UAF in zram_bvec_write_partial() and drop dead bio plumbing#891
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zram: fix UAF in zram_bvec_write_partial() and drop dead bio plumbing#891blktests-ci[bot] wants to merge 2 commits into
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May 27, 2026 07:29
zram_read_page() picks the sync or async backing device read path based on whether the parent bio is NULL. zram_bvec_write_partial() passes its parent bio down, so for ZRAM_WB slots the read is dispatched asynchronously and zram_read_page() returns 0 while the bio is still in flight. The caller then runs memcpy_from_bvec(), zram_write_page() and __free_page() on the buffer, leaving the async read to write into a freed page. zram_bvec_read_partial() was switched to NULL in commit 4e3c87b ("zram: fix synchronous reads") for the same reason; the write_partial counterpart was missed. Fixes: 4e3c87b ("zram: fix synchronous reads") Cc: Christoph Hellwig <hch@lst.de> Cc: stable@vger.kernel.org Signed-off-by: Cunlong Li <shenxiaogll@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
After the previous fix, zram_bvec_write_partial() always passes NULL to zram_read_page() and no longer needs the parent bio. Mirror the read side (zram_bvec_read_partial() has not taken a bio since commit 4e3c87b ("zram: fix synchronous reads")) and drop the parameter from zram_bvec_write_partial() and zram_bvec_write(). No functional change. Signed-off-by: Cunlong Li <shenxiaogll@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
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Pull request for series with
subject: zram: fix UAF in zram_bvec_write_partial() and drop dead bio plumbing
version: 2
url: https://patchwork.kernel.org/project/linux-block/list/?series=1101371