Currently XFS calls file_remove_privs() without holding i_mutex. This is
wrong because that function can end up messing with file permissions and
security xattrs for which we need i_mutex held.
Fix the problem by grabbing iolock exclusively when we will need to
change anything in permissions / xattrs.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/xfs/xfs_file.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 5c9e8296ebb3..c6622aa1f8af 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -521,6 +521,13 @@ restart:
if (error)
return error;
+ /* For changing security info in file_remove_privs() we need i_mutex */
+ if (*iolock == XFS_IOLOCK_SHARED && !IS_NOSEC(inode)) {
+ xfs_rw_iunlock(ip, *iolock);
+ *iolock = XFS_IOLOCK_EXCL;
+ xfs_rw_ilock(ip, *iolock);
+ goto restart;
+ }
/*
* If the offset is beyond the size of the file, we need to zero any
* blocks that fall between the existing EOF and the start of this
@@ -557,7 +564,9 @@ restart:
* setgid bits if the process is not being run by root. This keeps
* people from modifying setuid and setgid binaries.
*/
- return file_remove_privs(file);
+ if (!IS_NOSEC(inode))
+ return file_remove_privs(file);
+ return 0;
}
/*
--
1.8.4.5
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