The patch titled
Subject: nilfs2: fix use-after-free of nilfs_root in dirtying inodes via iput
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
nilfs2-fix-use-after-free-of-nilfs_root-in-dirtying-inodes-via-iput.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/nilfs2-fix-use-after-free-of-nilfs_root-in-dirtying-inodes-via-iput.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Subject: nilfs2: fix use-after-free of nilfs_root in dirtying inodes via iput
Date: Sat, 29 Jul 2023 04:13:18 +0900
During unmount process of nilfs2, nothing holds nilfs_root structure after
nilfs2 detaches its writer in nilfs_detach_log_writer(). Previously,
nilfs_evict_inode() could cause use-after-free read for nilfs_root if
inodes are left in "garbage_list" and released by nilfs_dispose_list at
the end of nilfs_detach_log_writer(), and this bug was fixed by commit
9b5a04ac3ad9 ("nilfs2: fix use-after-free bug of nilfs_root in
nilfs_evict_inode()").
However, it turned out that there is another possibility of UAF in the
call path where mark_inode_dirty_sync() is called from iput():
nilfs_detach_log_writer()
nilfs_dispose_list()
iput()
mark_inode_dirty_sync()
__mark_inode_dirty()
nilfs_dirty_inode()
__nilfs_mark_inode_dirty()
nilfs_load_inode_block() --> causes UAF of nilfs_root struct
This can happen after commit 0ae45f63d4ef ("vfs: add support for a
lazytime mount option"), which changed iput() to call
mark_inode_dirty_sync() on its final reference if i_state has I_DIRTY_TIME
flag and i_nlink is non-zero.
This issue appears after commit 28a65b49eb53 ("nilfs2: do not write dirty
data after degenerating to read-only") when using the syzbot reproducer,
but the issue has potentially existed before.
Fix this issue by adding a "purging flag" to the nilfs structure, setting
that flag while disposing the "garbage_list" and checking it in
__nilfs_mark_inode_dirty().
Unlike commit 9b5a04ac3ad9 ("nilfs2: fix use-after-free bug of nilfs_root
in nilfs_evict_inode()"), this patch does not rely on ns_writer to
determine whether to skip operations, so as not to break recovery on
mount. The nilfs_salvage_orphan_logs routine dirties the buffer of
salvaged data before attaching the log writer, so changing
__nilfs_mark_inode_dirty() to skip the operation when ns_writer is NULL
will cause recovery write to fail. The purpose of using the cleanup-only
flag is to allow for narrowing of such conditions.
Link: https://lkml.kernel.org/r/20230728191318.33047-1-konishi.ryusuke@xxxxxxxxx
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Reported-by: syzbot+74db8b3087f293d3a13a@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://lkml.kernel.org/r/000000000000b4e906060113fd63@xxxxxxxxxx
Fixes: 0ae45f63d4ef ("vfs: add support for a lazytime mount option")
Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 4.0+
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/inode.c | 8 ++++++++
fs/nilfs2/segment.c | 2 ++
fs/nilfs2/the_nilfs.h | 2 ++
3 files changed, 12 insertions(+)
--- a/fs/nilfs2/inode.c~nilfs2-fix-use-after-free-of-nilfs_root-in-dirtying-inodes-via-iput
+++ a/fs/nilfs2/inode.c
@@ -1101,9 +1101,17 @@ int nilfs_set_file_dirty(struct inode *i
int __nilfs_mark_inode_dirty(struct inode *inode, int flags)
{
+ struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
struct buffer_head *ibh;
int err;
+ /*
+ * Do not dirty inodes after the log writer has been detached
+ * and its nilfs_root struct has been freed.
+ */
+ if (unlikely(nilfs_purging(nilfs)))
+ return 0;
+
err = nilfs_load_inode_block(inode, &ibh);
if (unlikely(err)) {
nilfs_warn(inode->i_sb,
--- a/fs/nilfs2/segment.c~nilfs2-fix-use-after-free-of-nilfs_root-in-dirtying-inodes-via-iput
+++ a/fs/nilfs2/segment.c
@@ -2845,6 +2845,7 @@ void nilfs_detach_log_writer(struct supe
nilfs_segctor_destroy(nilfs->ns_writer);
nilfs->ns_writer = NULL;
}
+ set_nilfs_purging(nilfs);
/* Force to free the list of dirty files */
spin_lock(&nilfs->ns_inode_lock);
@@ -2857,4 +2858,5 @@ void nilfs_detach_log_writer(struct supe
up_write(&nilfs->ns_segctor_sem);
nilfs_dispose_list(nilfs, &garbage_list, 1);
+ clear_nilfs_purging(nilfs);
}
--- a/fs/nilfs2/the_nilfs.h~nilfs2-fix-use-after-free-of-nilfs_root-in-dirtying-inodes-via-iput
+++ a/fs/nilfs2/the_nilfs.h
@@ -29,6 +29,7 @@ enum {
THE_NILFS_DISCONTINUED, /* 'next' pointer chain has broken */
THE_NILFS_GC_RUNNING, /* gc process is running */
THE_NILFS_SB_DIRTY, /* super block is dirty */
+ THE_NILFS_PURGING, /* disposing dirty files for cleanup */
};
/**
@@ -208,6 +209,7 @@ THE_NILFS_FNS(INIT, init)
THE_NILFS_FNS(DISCONTINUED, discontinued)
THE_NILFS_FNS(GC_RUNNING, gc_running)
THE_NILFS_FNS(SB_DIRTY, sb_dirty)
+THE_NILFS_FNS(PURGING, purging)
/*
* Mount option operations
_
Patches currently in -mm which might be from konishi.ryusuke@xxxxxxxxx are
nilfs2-fix-use-after-free-of-nilfs_root-in-dirtying-inodes-via-iput.patch
