diff mbox series

[v6,2/5] fs: split off setxattr_setup function from setxattr

Message ID 20211222210127.958902-3-shr@fb.com (mailing list archive)
State New, archived
Headers show
Series io_uring: add xattr support | expand

Commit Message

Stefan Roesch Dec. 22, 2021, 9:01 p.m. UTC 
This splits of the setup part of the function
setxattr in its own dedicated function called
setxattr_setup.

This makes it possible to call this function
from io_uring in the pre-processing of an
xattr request.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
 fs/internal.h | 17 ++++++++++++
 fs/xattr.c    | 75 ++++++++++++++++++++++++++++++++++-----------------
 2 files changed, 67 insertions(+), 25 deletions(-)

Comments

Christian Brauner Dec. 23, 2021, 10:24 a.m. UTC | #1 
On Wed, Dec 22, 2021 at 01:01:24PM -0800, Stefan Roesch wrote:
> This splits of the setup part of the function
> setxattr in its own dedicated function called
> setxattr_setup.
> 
> This makes it possible to call this function
> from io_uring in the pre-processing of an
> xattr request.
> 
> Signed-off-by: Stefan Roesch <shr@fb.com>
> ---

I like the introduction of struct xattr_ctx.
But I would prefer if we called this setxattr_prepare() to mirror
setattr_prepare() and change the signature to:

int setxattr_setup(struct user_namespace *mnt_userns,
                   const char __user *name,
		   struct xattr_ctx *ctx,
		   void **xattr_val);

Since NULL is a success condition I think it makes more sense to have an
error returned and the value be a return argument. So sm like
(uncompiled and untested):

int setxattr_prepare(struct user_namespace *mnt_userns, const char __user *name,
		     struct xattr_ctx *ctx, void **xattr_val)
{
	void *kvalue = NULL;
	int error;

	if (ctx->flags & ~(XATTR_CREATE | XATTR_REPLACE))
		return -EINVAL;

	error = strncpy_from_user(ctx->kname, name, ctx->kname_sz);
	if (error == 0 || error == ctx->kname_sz)
		return -ERANGE;
	if (error < 0)
		return error;

	if (ctx->size) {
		if (ctx->size > XATTR_SIZE_MAX)
			return -E2BIG;

		kvalue = kvmalloc(ctx->size, GFP_KERNEL);
		if (!kvalue)
			return -ENOMEM;

		if (copy_from_user(kvalue, ctx->value, ctx->size)) {
			kvfree(kvalue);
			return -EFAULT;
		}

		if ((strcmp(ctx->kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
		    (strcmp(ctx->kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
			posix_acl_fix_xattr_from_user(mnt_userns, kvalue, ctx->size);
	}

	*xattr_val = kvalue;
	return 0;
}
diff mbox series

Patch

diff --git a/fs/internal.h b/fs/internal.h
index 432ea3ce76ec..e7d5b4a9fb43 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -202,3 +202,20 @@  struct linux_dirent64;
 
 int vfs_getdents(struct file *file, struct linux_dirent64 __user *dirent,
 		 unsigned int count, loff_t *pos);
+
+ /*
+  * fs/xattr.c:
+  */
+struct xattr_ctx {
+	/* Value of attribute */
+	const void __user *value;
+	size_t size;
+	/* Attribute name */
+	char *kname;
+	int kname_sz;
+	unsigned int flags;
+};
+
+void *setxattr_setup(struct user_namespace *mnt_userns,
+		     const char __user *name,
+		     struct xattr_ctx *ctx);
diff --git a/fs/xattr.c b/fs/xattr.c
index 5c8c5175b385..79afea64d7ba 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -25,6 +25,8 @@ 
 
 #include <linux/uaccess.h>
 
+#include "internal.h"
+
 static const char *
 strcmp_prefix(const char *a, const char *a_prefix)
 {
@@ -539,43 +541,66 @@  EXPORT_SYMBOL_GPL(vfs_removexattr);
 /*
  * Extended attribute SET operations
  */
-static long
-setxattr(struct user_namespace *mnt_userns, struct dentry *d,
-	 const char __user *name, const void __user *value, size_t size,
-	 int flags)
+
+void *setxattr_setup(struct user_namespace *mnt_userns, const char __user *name,
+		struct xattr_ctx *ctx)
 {
-	int error;
 	void *kvalue = NULL;
-	char kname[XATTR_NAME_MAX + 1];
+	int error;
 
-	if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
-		return -EINVAL;
+	if (ctx->flags & ~(XATTR_CREATE|XATTR_REPLACE))
+		return ERR_PTR(-EINVAL);
 
-	error = strncpy_from_user(kname, name, sizeof(kname));
-	if (error == 0 || error == sizeof(kname))
-		error = -ERANGE;
+	error = strncpy_from_user(ctx->kname, name, ctx->kname_sz);
+	if (error == 0 || error == ctx->kname_sz)
+		return  ERR_PTR(-ERANGE);
 	if (error < 0)
-		return error;
+		return ERR_PTR(error);
 
-	if (size) {
-		if (size > XATTR_SIZE_MAX)
-			return -E2BIG;
-		kvalue = kvmalloc(size, GFP_KERNEL);
+	if (ctx->size) {
+		if (ctx->size > XATTR_SIZE_MAX)
+			return ERR_PTR(-E2BIG);
+
+		kvalue = kvmalloc(ctx->size, GFP_KERNEL);
 		if (!kvalue)
-			return -ENOMEM;
-		if (copy_from_user(kvalue, value, size)) {
-			error = -EFAULT;
-			goto out;
+			return ERR_PTR(-ENOMEM);
+
+		if (copy_from_user(kvalue, ctx->value, ctx->size)) {
+			kvfree(kvalue);
+			return ERR_PTR(-EFAULT);
 		}
-		if ((strcmp(kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
-		    (strcmp(kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
-			posix_acl_fix_xattr_from_user(mnt_userns, kvalue, size);
+
+		if ((strcmp(ctx->kname, XATTR_NAME_POSIX_ACL_ACCESS) == 0) ||
+		    (strcmp(ctx->kname, XATTR_NAME_POSIX_ACL_DEFAULT) == 0))
+			posix_acl_fix_xattr_from_user(mnt_userns, kvalue, ctx->size);
 	}
 
+	return kvalue;
+}
+
+static long
+setxattr(struct user_namespace *mnt_userns, struct dentry *d,
+	const char __user *name, const void __user *value, size_t size,
+	int flags)
+{
+	char kname[XATTR_NAME_MAX + 1];
+	struct xattr_ctx ctx = {
+		.value    = value,
+		.size     = size,
+		.kname    = kname,
+		.kname_sz = sizeof(kname),
+		.flags    = flags,
+	};
+	void *kvalue;
+	int error;
+
+	kvalue = setxattr_setup(mnt_userns, name, &ctx);
+	if (IS_ERR(kvalue))
+		return PTR_ERR(kvalue);
+
 	error = vfs_setxattr(mnt_userns, d, kname, kvalue, size, flags);
-out:
-	kvfree(kvalue);
 
+	kvfree(kvalue);
 	return error;
 }