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Date: Mon, 7 Sep 2009 14:04:05 -0700 (PDT)
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Al Viro <viro@...iv.linux.org.uk>,
Linux Filesystem Mailing List <linux-fsdevel@...r.kernel.org>
cc: Eric Paris <eparis@...hat.com>, Mimi Zohar <zohar@...ibm.com>,
James Morris <jmorris@...ei.org>
Subject: [PATCH 5/8] Make 'check_acl()' a first-class filesystem op
From: Linus Torvalds <torvalds@...ux-foundation.org>
Date: Fri, 28 Aug 2009 11:51:25 -0700
This is stage one in flattening out the callchains for the common
permission testing. Rather than have most filesystem implemnt their
inode->i_op->permission own function that just calls back down to the
VFS layers 'generic_permission()' with the per-filesystem ACL checking
function, the filesystem can just expose its 'check_acl' function
directly, and let the VFS layer do everything for it.
This is all just preparatory - no filesystem actually enables this yet.
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
---
fs/namei.c | 62 +++++++++++++++++++++++++++++----------------------
include/linux/fs.h | 1 +
2 files changed, 36 insertions(+), 27 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index 7959e70..5953913 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -169,19 +169,10 @@ void putname(const char *name)
EXPORT_SYMBOL(putname);
#endif
-
-/**
- * generic_permission - check for access rights on a Posix-like filesystem
- * @inode: inode to check access rights for
- * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
- * @check_acl: optional callback to check for Posix ACLs
- *
- * Used to check for read/write/execute permissions on a file.
- * We use "fsuid" for this, letting us set arbitrary permissions
- * for filesystem access without changing the "normal" uids which
- * are used for other things..
+/*
+ * This does basic POSIX ACL permission checking
*/
-int generic_permission(struct inode *inode, int mask,
+static int acl_permission_check(struct inode *inode, int mask,
int (*check_acl)(struct inode *inode, int mask))
{
umode_t mode = inode->i_mode;
@@ -193,9 +184,7 @@ int generic_permission(struct inode *inode, int mask,
else {
if (IS_POSIXACL(inode) && (mode & S_IRWXG) && check_acl) {
int error = check_acl(inode, mask);
- if (error == -EACCES)
- goto check_capabilities;
- else if (error != -EAGAIN)
+ if (error != -EAGAIN)
return error;
}
@@ -208,8 +197,32 @@ int generic_permission(struct inode *inode, int mask,
*/
if ((mask & ~mode) == 0)
return 0;
+ return -EACCES;
+}
+
+/**
+ * generic_permission - check for access rights on a Posix-like filesystem
+ * @inode: inode to check access rights for
+ * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ * @check_acl: optional callback to check for Posix ACLs
+ *
+ * Used to check for read/write/execute permissions on a file.
+ * We use "fsuid" for this, letting us set arbitrary permissions
+ * for filesystem access without changing the "normal" uids which
+ * are used for other things..
+ */
+int generic_permission(struct inode *inode, int mask,
+ int (*check_acl)(struct inode *inode, int mask))
+{
+ int ret;
+
+ /*
+ * Do the basic POSIX ACL permission checks.
+ */
+ ret = acl_permission_check(inode, mask, check_acl);
+ if (ret != -EACCES)
+ return ret;
- check_capabilities:
/*
* Read/write DACs are always overridable.
* Executable DACs are overridable if at least one exec bit is set.
@@ -262,7 +275,7 @@ int inode_permission(struct inode *inode, int mask)
if (inode->i_op->permission)
retval = inode->i_op->permission(inode, mask);
else
- retval = generic_permission(inode, mask, NULL);
+ retval = generic_permission(inode, mask, inode->i_op->check_acl);
if (retval)
return retval;
@@ -432,27 +445,22 @@ static struct dentry * cached_lookup(struct dentry * parent, struct qstr * name,
*/
static int exec_permission_lite(struct inode *inode)
{
- umode_t mode = inode->i_mode;
+ int ret;
if (inode->i_op->permission) {
- int ret = inode->i_op->permission(inode, MAY_EXEC);
+ ret = inode->i_op->permission(inode, MAY_EXEC);
if (!ret)
goto ok;
return ret;
}
-
- if (current_fsuid() == inode->i_uid)
- mode >>= 6;
- else if (in_group_p(inode->i_gid))
- mode >>= 3;
-
- if (mode & MAY_EXEC)
+ ret = acl_permission_check(inode, MAY_EXEC, inode->i_op->check_acl);
+ if (!ret)
goto ok;
if (capable(CAP_DAC_OVERRIDE) || capable(CAP_DAC_READ_SEARCH))
goto ok;
- return -EACCES;
+ return ret;
ok:
return security_inode_permission(inode, MAY_EXEC);
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 73e9b64..c1f9935 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1528,6 +1528,7 @@ struct inode_operations {
void (*put_link) (struct dentry *, struct nameidata *, void *);
void (*truncate) (struct inode *);
int (*permission) (struct inode *, int);
+ int (*check_acl)(struct inode *, int);
int (*setattr) (struct dentry *, struct iattr *);
int (*getattr) (struct vfsmount *mnt, struct dentry *, struct kstat *);
int (*setxattr) (struct dentry *, const char *,const void *,size_t,int);
--
1.6.4.1.209.g74b8
--
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