On Fri 26-04-24 18:20:14, Christian Göttsche wrote:
From: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
Add the four syscalls setxattrat(), getxattrat(), listxattrat() and
removexattrat(). Those can be used to operate on extended attributes,
especially security related ones, either relative to a pinned directory
or on a file descriptor without read access, avoiding a
/proc/<pid>/fd/<fd> detour, requiring a mounted procfs.
One use case will be setfiles(8) setting SELinux file contexts
("security.selinux") without race conditions and without a file
descriptor opened with read access requiring SELinux read permission.
Use the do_{name}at() pattern from fs/open.c.
Pass the value of the extended attribute, its length, and for
setxattrat(2) the command (XATTR_CREATE or XATTR_REPLACE) via an added
struct xattr_args to not exceed six syscall arguments and not
merging the AT_* and XATTR_* flags.
Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
The patch looks good to me. Just a few nits below:
-static int path_setxattr(const char __user *pathname,
+static int do_setxattrat(int dfd, const char __user *pathname, unsigned int at_flags,
Can we please stay within 80 columns (happens in multiple places in the
patch)? I don't insist but it makes things easier to read in some setups so
I prefer it.
@@ -852,13 +908,21 @@ listxattr(struct dentry *d, char __user *list, size_t size)
return error;
}
-static ssize_t path_listxattr(const char __user *pathname, char __user *list,
- size_t size, unsigned int lookup_flags)
+static ssize_t do_listxattrat(int dfd, const char __user *pathname, char __user *list,
+ size_t size, int flags)
So I like how in previous syscalls you have 'at_flags', 'lookup_flags', and
'xattr_flags'. That makes things much easier to digest. Can you please stay
with that convention here as well and call this argument 'at_flags'? Also I
think the argument ordering like "dfd, pathname, at_flags, list, size" is
more consistent with other syscalls you define.
@@ -870,16 +934,22 @@ static ssize_t path_listxattr(const char __user *pathname, char __user *list,
return error;
}
+SYSCALL_DEFINE5(listxattrat, int, dfd, const char __user *, pathname, char __user *, list,
+ size_t, size, int, flags)
+{
+ return do_listxattrat(dfd, pathname, list, size, flags);
+}
+
Same comment as above - "flags" -> "at_flags" and reorder args please.
@@ -917,13 +987,21 @@ removexattr(struct mnt_idmap *idmap, struct dentry *d,
return vfs_removexattr(idmap, d, kname);
}
-static int path_removexattr(const char __user *pathname,
- const char __user *name, unsigned int lookup_flags)
+static int do_removexattrat(int dfd, const char __user *pathname,
+ const char __user *name, int flags)
{
Same comment as above - "flags" -> "at_flags" and reorder args please.
@@ -939,16 +1017,22 @@ static int path_removexattr(const char __user *pathname,
return error;
}
+SYSCALL_DEFINE4(removexattrat, int, dfd, const char __user *, pathname,
+ const char __user *, name, int, flags)
+{
Same comment as above - "flags" -> "at_flags" and reorder args please.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
