From: Zhang Yi <yi.zhang@xxxxxxxxxx>
The EXT4_IOC_GET_ES_CACHE and EXT4_IOC_PRECACHE_EXTENTS currently
invokes ext4_ext_precache() to preload the extent cache without holding
the inode's i_rwsem. This can result in stale extent cache entries when
competing with operations such as ext4_collapse_range() which calls
ext4_ext_remove_space() or ext4_ext_shift_extents().
The problem arises when ext4_ext_remove_space() temporarily releases
i_data_sem due to insufficient journal credits. During this interval, a
concurrent EXT4_IOC_GET_ES_CACHE or EXT4_IOC_PRECACHE_EXTENTS may cache
extent entries that are about to be deleted. As a result, these cached
entries become stale and inconsistent with the actual extents.
Loading the extents cache without holding the inode's i_rwsem or the
mapping's invalidate_lock is not permitted besides during the writeback.
Fix this by holding the i_rwsem during EXT4_IOC_GET_ES_CACHE and
EXT4_IOC_PRECACHE_EXTENTS.
Signed-off-by: Zhang Yi <yi.zhang@xxxxxxxxxx>
---
fs/ext4/extents.c | 2 ++
fs/ext4/ioctl.c | 8 +++++++-
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 3adf05fbdd59..b5eb89ef7ae2 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -5011,7 +5011,9 @@ int ext4_get_es_cache(struct inode *inode, struct fiemap_extent_info *fieinfo,
}
if (fieinfo->fi_flags & FIEMAP_FLAG_CACHE) {
+ inode_lock_shared(inode);
error = ext4_ext_precache(inode);
+ inode_unlock_shared(inode);
if (error)
return error;
fieinfo->fi_flags &= ~FIEMAP_FLAG_CACHE;
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index d17207386ead..0e240013c84d 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -1505,8 +1505,14 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
return 0;
}
case EXT4_IOC_PRECACHE_EXTENTS:
- return ext4_ext_precache(inode);
+ {
+ int ret;
+ inode_lock_shared(inode);
+ ret = ext4_ext_precache(inode);
+ inode_unlock_shared(inode);
+ return ret;
+ }
case FS_IOC_SET_ENCRYPTION_POLICY:
if (!ext4_has_feature_encrypt(sb))
return -EOPNOTSUPP;
--
2.46.1
