* [PATCH v2] fs: add a new SB_NOUMASK flag
@ 2023-09-10 19:30 Jeff Layton
2023-09-11 13:42 ` Christian Brauner
0 siblings, 1 reply; 2+ messages in thread
From: Jeff Layton @ 2023-09-10 19:30 UTC (permalink / raw)
To: Alexander Viro, Christian Brauner, Trond Myklebust,
Anna Schumaker, Ondrej Valousek
Cc: linux-fsdevel, linux-kernel, linux-nfs, Jeff Layton
SB_POSIXACL must be set when a filesystem supports POSIX ACLs, but NFSv4
also sets this flag to prevent the VFS from applying the umask on
newly-created files. NFSv4 doesn't support POSIX ACLs however, which
causes confusion when other subsystems try to test for them.
Split the umask-stripping opt-out into a separate SB_NOUMASK flag, and
have NFSv4 set that instead of SB_POSIXACL. Fix the appropriate places
in the VFS to check for that flag (in addition to SB_POSIXACL) when
stripping the umask.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
Yet another approach to fixing this issue. I think this way is probably
the best, since makes the purpose of these flags clearer, and stops NFS
from relying on SB_POSIXACL to avoid umask stripping.
---
Changes in v2:
- new approach: add a new SB_NOUMASK flag that NFSv4 can use instead of
SB_POSIXACL
- Link to v1: https://lore.kernel.org/r/20230908-acl-fix-v1-1-1e6b76c8dcc8@kernel.org
---
fs/init.c | 4 ++--
fs/namei.c | 2 +-
fs/nfs/super.c | 2 +-
include/linux/fs.h | 4 +++-
4 files changed, 7 insertions(+), 5 deletions(-)
diff --git a/fs/init.c b/fs/init.c
index 9684406a8416..157404bb7d19 100644
--- a/fs/init.c
+++ b/fs/init.c
@@ -153,7 +153,7 @@ int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
if (IS_ERR(dentry))
return PTR_ERR(dentry);
- if (!IS_POSIXACL(path.dentry->d_inode))
+ if (!IS_NOUMASK(path.dentry->d_inode))
mode &= ~current_umask();
error = security_path_mknod(&path, dentry, mode, dev);
if (!error)
@@ -229,7 +229,7 @@ int __init init_mkdir(const char *pathname, umode_t mode)
dentry = kern_path_create(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
if (IS_ERR(dentry))
return PTR_ERR(dentry);
- if (!IS_POSIXACL(path.dentry->d_inode))
+ if (!IS_NOUMASK(path.dentry->d_inode))
mode &= ~current_umask();
error = security_path_mkdir(&path, dentry, mode);
if (!error)
diff --git a/fs/namei.c b/fs/namei.c
index 567ee547492b..905fdfec5d26 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3117,7 +3117,7 @@ EXPORT_SYMBOL(unlock_rename);
*/
static inline umode_t mode_strip_umask(const struct inode *dir, umode_t mode)
{
- if (!IS_POSIXACL(dir))
+ if (!IS_NOUMASK(dir))
mode &= ~current_umask();
return mode;
}
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 0d6473cb00cb..81cd11c4db3d 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -1071,7 +1071,7 @@ static void nfs_fill_super(struct super_block *sb, struct nfs_fs_context *ctx)
sb->s_export_op = &nfs_export_ops;
break;
case 4:
- sb->s_flags |= SB_POSIXACL;
+ sb->s_flags |= SB_NOUMASK;
sb->s_time_gran = 1;
sb->s_time_min = S64_MIN;
sb->s_time_max = S64_MAX;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4aeb3fa11927..51ad013ca716 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1119,13 +1119,14 @@ extern int send_sigurg(struct fown_struct *fown);
#define SB_NOATIME BIT(10) /* Do not update access times. */
#define SB_NODIRATIME BIT(11) /* Do not update directory access times */
#define SB_SILENT BIT(15)
-#define SB_POSIXACL BIT(16) /* VFS does not apply the umask */
+#define SB_POSIXACL BIT(16) /* POSIX ACLs are supported (implies NOUMASK) */
#define SB_INLINECRYPT BIT(17) /* Use blk-crypto for encrypted files */
#define SB_KERNMOUNT BIT(22) /* this is a kern_mount call */
#define SB_I_VERSION BIT(23) /* Update inode I_version field */
#define SB_LAZYTIME BIT(25) /* Update the on-disk [acm]times lazily */
/* These sb flags are internal to the kernel */
+#define SB_NOUMASK BIT(20) /* VFS does not apply the umask */
#define SB_DEAD BIT(21)
#define SB_DYING BIT(24)
#define SB_SUBMOUNT BIT(26)
@@ -2111,6 +2112,7 @@ static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags
#define IS_APPEND(inode) ((inode)->i_flags & S_APPEND)
#define IS_IMMUTABLE(inode) ((inode)->i_flags & S_IMMUTABLE)
#define IS_POSIXACL(inode) __IS_FLG(inode, SB_POSIXACL)
+#define IS_NOUMASK(inode) __IS_FLG(inode, SB_POSIXACL|SB_NOUMASK)
#define IS_DEADDIR(inode) ((inode)->i_flags & S_DEAD)
#define IS_NOCMTIME(inode) ((inode)->i_flags & S_NOCMTIME)
---
base-commit: a48fa7efaf1161c1c898931fe4c7f0070964233a
change-id: 20230908-acl-fix-6f8f86930f32
Best regards,
--
Jeff Layton <jlayton@kernel.org>
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v2] fs: add a new SB_NOUMASK flag
2023-09-10 19:30 [PATCH v2] fs: add a new SB_NOUMASK flag Jeff Layton
@ 2023-09-11 13:42 ` Christian Brauner
0 siblings, 0 replies; 2+ messages in thread
From: Christian Brauner @ 2023-09-11 13:42 UTC (permalink / raw)
To: Jeff Layton
Cc: Alexander Viro, Trond Myklebust, Anna Schumaker, Ondrej Valousek,
linux-fsdevel, linux-kernel, linux-nfs
On Sun, Sep 10, 2023 at 03:30:48PM -0400, Jeff Layton wrote:
> SB_POSIXACL must be set when a filesystem supports POSIX ACLs, but NFSv4
> also sets this flag to prevent the VFS from applying the umask on
> newly-created files. NFSv4 doesn't support POSIX ACLs however, which
> causes confusion when other subsystems try to test for them.
>
> Split the umask-stripping opt-out into a separate SB_NOUMASK flag, and
> have NFSv4 set that instead of SB_POSIXACL. Fix the appropriate places
> in the VFS to check for that flag (in addition to SB_POSIXACL) when
> stripping the umask.
Oh, I see you only raised SB_POSIXACL to avoid umask stripping. That's a
bit weird indeed. Hm, since this is an internal, non-user changeable
flag I think it might be better in s_iflags as SB_I_NOUMASK? Also allows
us to avoid wasting an s_flags bit.
>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
> Yet another approach to fixing this issue. I think this way is probably
> the best, since makes the purpose of these flags clearer, and stops NFS
> from relying on SB_POSIXACL to avoid umask stripping.
> ---
> Changes in v2:
> - new approach: add a new SB_NOUMASK flag that NFSv4 can use instead of
> SB_POSIXACL
> - Link to v1: https://lore.kernel.org/r/20230908-acl-fix-v1-1-1e6b76c8dcc8@kernel.org
> ---
> fs/init.c | 4 ++--
> fs/namei.c | 2 +-
> fs/nfs/super.c | 2 +-
> include/linux/fs.h | 4 +++-
> 4 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/fs/init.c b/fs/init.c
> index 9684406a8416..157404bb7d19 100644
> --- a/fs/init.c
> +++ b/fs/init.c
> @@ -153,7 +153,7 @@ int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
> if (IS_ERR(dentry))
> return PTR_ERR(dentry);
>
> - if (!IS_POSIXACL(path.dentry->d_inode))
> + if (!IS_NOUMASK(path.dentry->d_inode))
> mode &= ~current_umask();
> error = security_path_mknod(&path, dentry, mode, dev);
> if (!error)
> @@ -229,7 +229,7 @@ int __init init_mkdir(const char *pathname, umode_t mode)
> dentry = kern_path_create(AT_FDCWD, pathname, &path, LOOKUP_DIRECTORY);
> if (IS_ERR(dentry))
> return PTR_ERR(dentry);
> - if (!IS_POSIXACL(path.dentry->d_inode))
> + if (!IS_NOUMASK(path.dentry->d_inode))
> mode &= ~current_umask();
Could you please just convert them over to mode_strip_umask()?
Seems I forgot these two places back then.
^ permalink raw reply [flat|nested] 2+ messages in thread
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