On 3/3/15 4:38 AM, Jan Kara wrote:
> 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>
This seems like it stands alone, modulo the file_remove_privs function
renaming... should it just be pulled into XFS by Dave? I guess that would
require the renaming patch to be rebased...
Thanks,
-Eric
> ---
> 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 fa81a43702ee..3d601e92bd44 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -563,6 +563,13 @@ 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
> @@ -601,7 +608,9 @@ 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;
> }
>
> /*
>
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