From d381d8a9a08cac9824096213069159be17fd2e2f Mon Sep 17 00:00:00 2001 From: James Morris Date: Sun, 30 Oct 2005 14:59:22 -0800 Subject: [PATCH] SELinux: canonicalize getxattr() This patch allows SELinux to canonicalize the value returned from getxattr() via the security_inode_getsecurity() hook, which is called after the fs level getxattr() function. The purpose of this is to allow the in-core security context for an inode to override the on-disk value. This could happen in cases such as upgrading a system to a different labeling form (e.g. standard SELinux to MLS) without needing to do a full relabel of the filesystem. In such cases, we want getxattr() to return the canonical security context that the kernel is using rather than what is stored on disk. The implementation hooks into the inode_getsecurity(), adding another parameter to indicate the result of the preceding fs-level getxattr() call, so that SELinux knows whether to compare a value obtained from disk with the kernel value. We also now allow getxattr() to work for mountpoint labeled filesystems (i.e. mount with option context=foo_t), as we are able to return the kernel value to the user. Signed-off-by: James Morris Signed-off-by: Stephen Smalley Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- security/dummy.c | 2 +- security/selinux/hooks.c | 46 ++++++++++++++++++++++++++++++++-------------- 2 files changed, 33 insertions(+), 15 deletions(-) (limited to 'security') diff --git a/security/dummy.c b/security/dummy.c index 3d34f3de7e8..2a0337a52d3 100644 --- a/security/dummy.c +++ b/security/dummy.c @@ -377,7 +377,7 @@ static int dummy_inode_removexattr (struct dentry *dentry, char *name) return 0; } -static int dummy_inode_getsecurity(struct inode *inode, const char *name, void *buffer, size_t size) +static int dummy_inode_getsecurity(struct inode *inode, const char *name, void *buffer, size_t size, int err) { return -EOPNOTSUPP; } diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 8cd33b2cd86..d9ec85292e1 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2208,9 +2208,6 @@ static int selinux_inode_getxattr (struct dentry *dentry, char *name) struct inode *inode = dentry->d_inode; struct superblock_security_struct *sbsec = inode->i_sb->s_security; - if (sbsec->behavior == SECURITY_FS_USE_MNTPOINT) - return -EOPNOTSUPP; - return dentry_has_perm(current, NULL, dentry, FILE__GETATTR); } @@ -2241,33 +2238,54 @@ static int selinux_inode_removexattr (struct dentry *dentry, char *name) return -EACCES; } -static int selinux_inode_getsecurity(struct inode *inode, const char *name, void *buffer, size_t size) +/* + * Copy the in-core inode security context value to the user. If the + * getxattr() prior to this succeeded, check to see if we need to + * canonicalize the value to be finally returned to the user. + * + * Permission check is handled by selinux_inode_getxattr hook. + */ +static int selinux_inode_getsecurity(struct inode *inode, const char *name, void *buffer, size_t size, int err) { struct inode_security_struct *isec = inode->i_security; char *context; unsigned len; int rc; - /* Permission check handled by selinux_inode_getxattr hook.*/ - - if (strcmp(name, XATTR_SELINUX_SUFFIX)) - return -EOPNOTSUPP; + if (strcmp(name, XATTR_SELINUX_SUFFIX)) { + rc = -EOPNOTSUPP; + goto out; + } rc = security_sid_to_context(isec->sid, &context, &len); if (rc) - return rc; + goto out; + /* Probe for required buffer size */ if (!buffer || !size) { - kfree(context); - return len; + rc = len; + goto out_free; } + if (size < len) { - kfree(context); - return -ERANGE; + rc = -ERANGE; + goto out_free; + } + + if (err > 0) { + if ((len == err) && !(memcmp(context, buffer, len))) { + /* Don't need to canonicalize value */ + rc = err; + goto out_free; + } + memset(buffer, 0, size); } memcpy(buffer, context, len); + rc = len; +out_free: kfree(context); - return len; +out: + return rc; } static int selinux_inode_setsecurity(struct inode *inode, const char *name, -- cgit v1.2.3-70-g09d2