Hello,
On Sat 13-07-19 06:11:59, Max Kellermann wrote:
Make IS_POSIXACL() return false if POSIX ACL support is disabled and ignore SB_POSIXACL/MS_POSIXACL.
Never skip applying the umask in namei.c and never bother to do any ACL specific checks if the filesystem falsely indicates it has ACLs enabled when the feature is completely disabled in the kernel.
This fixes a problem where the umask is always ignored in the NFS client when compiled without CONFIG_FS_POSIX_ACL. This is a 4 year old regression caused by commit 013cdf1088d723 which itself was not completely wrong, but failed to consider all the side effects by misdesigned VFS code.
Prior to that commit, there were two places where the umask could be applied, for example when creating a directory:
in the VFS layer in SYSCALL_DEFINE3(mkdirat), but only if !IS_POSIXACL()
again (unconditionally) in nfs3_proc_mkdir()
The first one does not apply, because even without CONFIG_FS_POSIX_ACL, the NFS client sets MS_POSIXACL in nfs_fill_super().
After that commit, (2.) was replaced by:
2b. in posix_acl_create(), called by nfs3_proc_mkdir()
There's one branch in posix_acl_create() which applies the umask; however, without CONFIG_FS_POSIX_ACL, posix_acl_create() is an empty dummy function which does not apply the umask.
The approach chosen by this patch is to make IS_POSIXACL() always return false when POSIX ACL support is disabled, so the umask always gets applied by the VFS layer. This is consistent with the (regular) behavior of posix_acl_create(): that function returns early if IS_POSIXACL() is false, before applying the umask.
Therefore, posix_acl_create() is responsible for applying the umask if there is ACL support enabled in the file system (SB_POSIXACL), and the VFS layer is responsible for all other cases (no SB_POSIXACL or no CONFIG_FS_POSIX_ACL).
Signed-off-by: Max Kellermann mk@cm4all.com Cc: stable@vger.kernel.org
Thanks for the patch. This patch definitely looks good to me so feel free to add:
Reviewed-by: Jan Kara jack@suse.cz
I just wonder, do you really need patches 1 and 2? Doesn't this patch alone fix the problem? Because AFAIU the problem, this patch should be enough and indeed the logic "VFS is responsible for applying umask if !IS_POSIXACL and otherwise posix_acl_create() is responsible for it" looks the most logical to me. BTW, I think you should add VFS maintainer - Al Viro viro@ZenIV.linux.org.uk - to CC to merge the patch.
Honza
include/linux/fs.h | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/include/linux/fs.h b/include/linux/fs.h index f7fdfe93e25d..5e9f3aa7ba26 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1993,7 +1993,12 @@ static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags #define IS_NOQUOTA(inode) ((inode)->i_flags & S_NOQUOTA) #define IS_APPEND(inode) ((inode)->i_flags & S_APPEND) #define IS_IMMUTABLE(inode) ((inode)->i_flags & S_IMMUTABLE)
+#ifdef CONFIG_FS_POSIX_ACL #define IS_POSIXACL(inode) __IS_FLG(inode, SB_POSIXACL) +#else +#define IS_POSIXACL(inode) 0 +#endif #define IS_DEADDIR(inode) ((inode)->i_flags & S_DEAD)
#define IS_NOCMTIME(inode) ((inode)->i_flags & S_NOCMTIME)
2.20.1