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f2fs: fix information leak in f2fs_move_inline_dirents()

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When converting an inline directory to a regular one, f2fs is leaking
uninitialized memory to disk because it doesn't initialize the entire
directory block.  Fix this by zero-initializing the block.

This bug was introduced by commit 4ec17d688d ("f2fs: avoid unneeded
initializing when converting inline dentry"), which didn't consider the
security implications of leaking uninitialized memory to disk.

This was found by running xfstest generic/435 on a KMSAN-enabled kernel.

Fixes: 4ec17d688d ("f2fs: avoid unneeded initializing when converting inline dentry")
Cc: <stable@vger.kernel.org> # v4.3+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Eric Biggers 2023-01-22 23:04:14 -08:00 committed by Jaegeuk Kim
parent b1b9896718
commit 9a5571cff4
1 changed files with 6 additions and 7 deletions
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13
fs/f2fs/inline.c
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@ -421,18 +421,17 @@ static int f2fs_move_inline_dirents(struct inode *dir, struct page *ipage,
dentry_blk = page_address(page);
/*
* Start by zeroing the full block, to ensure that all unused space is
* zeroed and no uninitialized memory is leaked to disk.
*/
memset(dentry_blk, 0, F2FS_BLKSIZE);
make_dentry_ptr_inline(dir, &src, inline_dentry);
make_dentry_ptr_block(dir, &dst, dentry_blk);
/* copy data from inline dentry block to new dentry block */
memcpy(dst.bitmap, src.bitmap, src.nr_bitmap);
memset(dst.bitmap + src.nr_bitmap, 0, dst.nr_bitmap - src.nr_bitmap);
/*
* we do not need to zero out remainder part of dentry and filename
* field, since we have used bitmap for marking the usage status of
* them, besides, we can also ignore copying/zeroing reserved space
* of dentry block, because them haven't been used so far.
*/
memcpy(dst.dentry, src.dentry, SIZE_OF_DIR_ENTRY * src.max);
memcpy(dst.filename, src.filename, src.max * F2FS_SLOT_LEN);