From: Pan Bian <bianpan2016@xxxxxxx> In nilfs_gccache_submit_read_data(), brelse(bh) is called to drop the reference count of bh when the call to nilfs_dat_translate() fails. If the reference count hits 0 and its owner page gets unlocked, bh may be freed. However, bh->b_page is dereferenced to put the page after that, which may result in a use-after-free bug. This patch moves the release operation after unlocking and putting the page. NOTE: The function in question is only called in GC, and in combination with current userland tools, address translation using DAT does not occur in that function, so the code path that causes this issue will not be executed. However, it is possible to run that code path by intentionally modifying the userland GC library or by calling the GC ioctl directly. Link: https://lkml.kernel.org/r/1543201709-53191-1-git-send-email-bianpan2016@xxxxxxx Signed-off-by: Pan Bian <bianpan2016@xxxxxxx> Reported-by: Ferry Meng <mengferry@xxxxxxxxxxxxxxxxx> Closes: https://lkml.kernel.org/r/20230818092022.111054-1-mengferry@xxxxxxxxxxxxxxxxx Fixes: a3d93f709e89 ("nilfs2: block cache for garbage collection") [konishi.ryusuke@xxxxxxxxx: NOTE added to the commit log] Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> --- fs/nilfs2/gcinode.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/nilfs2/gcinode.c b/fs/nilfs2/gcinode.c index 48fe71d309cb..8beb2730929d 100644 --- a/fs/nilfs2/gcinode.c +++ b/fs/nilfs2/gcinode.c @@ -73,10 +73,8 @@ int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff, struct the_nilfs *nilfs = inode->i_sb->s_fs_info; err = nilfs_dat_translate(nilfs->ns_dat, vbn, &pbn); - if (unlikely(err)) { /* -EIO, -ENOMEM, -ENOENT */ - brelse(bh); + if (unlikely(err)) /* -EIO, -ENOMEM, -ENOENT */ goto failed; - } } lock_buffer(bh); @@ -102,6 +100,8 @@ int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff, failed: unlock_page(bh->b_page); put_page(bh->b_page); + if (unlikely(err)) + brelse(bh); return err; } -- 2.34.1
