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Subject[PATCH] ext2: fix potential use after free
Date
The function ext2_xattr_set calls brelse(bh) to drop the reference count
of bh. After that, bh may be freed. However, following brelse(bh),
it reads bh->b_data via macro HDR(bh). This may result in a
use-after-free bug. This patch moves brelse(bh) after reading field.

Signed-off-by: Pan Bian <bianpan2016@163.com>
---
fs/ext2/xattr.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext2/xattr.c b/fs/ext2/xattr.c
index 62d9a659a..dd8f10d 100644
--- a/fs/ext2/xattr.c
+++ b/fs/ext2/xattr.c
@@ -612,9 +612,9 @@ bad_block: ext2_error(sb, "ext2_xattr_set",
}

cleanup:
- brelse(bh);
if (!(bh && header == HDR(bh)))
kfree(header);
+ brelse(bh);
up_write(&EXT2_I(inode)->xattr_sem);

return error;
--
2.7.4

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