5.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pan Bian <bianpan2016@xxxxxxx> commit 7ee29facd8a9c5a26079148e36bcf07141b3a6bc upstream. 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. [konishi.ryusuke@xxxxxxxxx: NOTE added to the commit log] Link: https://lkml.kernel.org/r/1543201709-53191-1-git-send-email-bianpan2016@xxxxxxx Link: https://lkml.kernel.org/r/20230921141731.10073-1-konishi.ryusuke@xxxxxxxxx Fixes: a3d93f709e89 ("nilfs2: block cache for garbage collection") Signed-off-by: Pan Bian <bianpan2016@xxxxxxx> Reported-by: Ferry Meng <mengferry@xxxxxxxxxxxxxxxxx> Closes: https://lkml.kernel.org/r/20230818092022.111054-1-mengferry@xxxxxxxxxxxxxxxxx Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/nilfs2/gcinode.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/fs/nilfs2/gcinode.c +++ b/fs/nilfs2/gcinode.c @@ -73,10 +73,8 @@ int nilfs_gccache_submit_read_data(struc 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(struc failed: unlock_page(bh->b_page); put_page(bh->b_page); + if (unlikely(err)) + brelse(bh); return err; }
