6.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Zhang Yi yi.zhang@huawei.com
[ Upstream commit f22a0ef2231a7d8374bb021eb86404d0e9de5a02 ]
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@huawei.com Link: https://patch.msgid.link/20250423085257.122685-6-yi.zhang@huaweicloud.com Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Sasha Levin sashal@kernel.org --- 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 81e010a6c797c..828a78a9600a8 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -4996,7 +4996,9 @@ 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 d17207386ead1..0e240013c84d2 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;