unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
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nilfs2: fix kernel bug on rename operation of broken directory

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Syzbot reported that in rename directory operation on broken directory on
nilfs2, __block_write_begin_int() called to prepare block write may fail
BUG_ON check for access exceeding the folio/page size.

This is because nilfs_dotdot(), which gets parent directory reference
entry ("..") of the directory to be moved or renamed, does not check
consistency enough, and may return location exceeding folio/page size for
broken directories.

Fix this issue by checking required directory entries ("." and "..") in
the first chunk of the directory in nilfs_dotdot().

Link: https://lkml.kernel.org/r/20240628165107.9006-1-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Reported-by: syzbot+d3abed1ad3d367fa2627@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d3abed1ad3d367fa2627
Fixes: 2ba466d74e ("nilfs2: directory entry operations")
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ryusuke Konishi 2024-06-29 01:51:07 +09:00 committed by Andrew Morton
parent bd225530a4
commit a9e1ddc09c
1 changed files with 30 additions and 2 deletions
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32
fs/nilfs2/dir.c
View file

@ -383,11 +383,39 @@ struct nilfs_dir_entry *nilfs_find_entry(struct inode *dir,
struct nilfs_dir_entry *nilfs_dotdot(struct inode *dir, struct folio **foliop)
{
struct nilfs_dir_entry *de = nilfs_get_folio(dir, 0, foliop);
struct folio *folio;
struct nilfs_dir_entry *de, *next_de;
size_t limit;
char *msg;
de = nilfs_get_folio(dir, 0, &folio);
if (IS_ERR(de))
return NULL;
return nilfs_next_entry(de);
limit = nilfs_last_byte(dir, 0); /* is a multiple of chunk size */
if (unlikely(!limit || le64_to_cpu(de->inode) != dir->i_ino ||
!nilfs_match(1, ".", de))) {
msg = "missing '.'";
goto fail;
}
next_de = nilfs_next_entry(de);
/*
* If "next_de" has not reached the end of the chunk, there is
* at least one more record. Check whether it matches "..".
*/
if (unlikely((char *)next_de == (char *)de + nilfs_chunk_size(dir) ||
!nilfs_match(2, "..", next_de))) {
msg = "missing '..'";
goto fail;
}
*foliop = folio;
return next_de;
fail:
nilfs_error(dir->i_sb, "directory #%lu %s", dir->i_ino, msg);
folio_release_kmap(folio, de);
return NULL;
}
ino_t nilfs_inode_by_name(struct inode *dir, const struct qstr *qstr)