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security: allow finer granularity in permitting copy-up of security xattrs

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Copying up xattrs is solely based on the security xattr name. For finer
granularity add a dentry parameter to the security_inode_copy_up_xattr
hook definition, allowing decisions to be based on the xattr content as
well.

Co-developed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Acked-by: Amir Goldstein <amir73il@gmail.com>
Acked-by: Paul Moore <paul@paul-moore.com> (LSM,SELinux)
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
This commit is contained in:
Stefan Berger 2024-02-23 12:25:05 -05:00 committed by Mimi Zohar
parent c21632b668
commit 3253804773
7 changed files with 11 additions and 9 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
fs/overlayfs/copy_up.c
View file

@ -114,7 +114,7 @@ int ovl_copy_xattr(struct super_block *sb, const struct path *oldpath, struct de
if (ovl_is_private_xattr(sb, name)) if (ovl_is_private_xattr(sb, name))
continue; continue;
error = security_inode_copy_up_xattr(name); error = security_inode_copy_up_xattr(old, name);
if (error < 0 && error != -EOPNOTSUPP) if (error < 0 && error != -EOPNOTSUPP)
break; break;
if (error == 1) { if (error == 1) {

3
include/linux/lsm_hook_defs.h
View file

@ -176,7 +176,8 @@ LSM_HOOK(int, 0, inode_listsecurity, struct inode *inode, char *buffer,
size_t buffer_size) size_t buffer_size)
LSM_HOOK(void, LSM_RET_VOID, inode_getsecid, struct inode *inode, u32 *secid) LSM_HOOK(void, LSM_RET_VOID, inode_getsecid, struct inode *inode, u32 *secid)
LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new) LSM_HOOK(int, 0, inode_copy_up, struct dentry *src, struct cred **new)
LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, const char *name) LSM_HOOK(int, -EOPNOTSUPP, inode_copy_up_xattr, struct dentry *src,
const char *name)
LSM_HOOK(int, 0, kernfs_init_security, struct kernfs_node *kn_dir, LSM_HOOK(int, 0, kernfs_init_security, struct kernfs_node *kn_dir,
struct kernfs_node *kn) struct kernfs_node *kn)
LSM_HOOK(int, 0, file_permission, struct file *file, int mask) LSM_HOOK(int, 0, file_permission, struct file *file, int mask)

4
include/linux/security.h
View file

@ -398,7 +398,7 @@ int security_inode_setsecurity(struct inode *inode, const char *name, const void
int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size); int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size);
void security_inode_getsecid(struct inode *inode, u32 *secid); void security_inode_getsecid(struct inode *inode, u32 *secid);
int security_inode_copy_up(struct dentry *src, struct cred **new); int security_inode_copy_up(struct dentry *src, struct cred **new);
int security_inode_copy_up_xattr(const char *name); int security_inode_copy_up_xattr(struct dentry *src, const char *name);
int security_kernfs_init_security(struct kernfs_node *kn_dir, int security_kernfs_init_security(struct kernfs_node *kn_dir,
struct kernfs_node *kn); struct kernfs_node *kn);
int security_file_permission(struct file *file, int mask); int security_file_permission(struct file *file, int mask);
@ -1016,7 +1016,7 @@ static inline int security_kernfs_init_security(struct kernfs_node *kn_dir,
return 0; return 0;
} }
static inline int security_inode_copy_up_xattr(const char *name) static inline int security_inode_copy_up_xattr(struct dentry *src, const char *name)
{ {
return -EOPNOTSUPP; return -EOPNOTSUPP;
} }

2
security/integrity/evm/evm_main.c
View file

@ -946,7 +946,7 @@ static void evm_inode_post_setattr(struct mnt_idmap *idmap,
evm_update_evmxattr(dentry, NULL, NULL, 0); evm_update_evmxattr(dentry, NULL, NULL, 0);
} }
static int evm_inode_copy_up_xattr(const char *name) static int evm_inode_copy_up_xattr(struct dentry *src, const char *name)
{ {
if (strcmp(name, XATTR_NAME_EVM) == 0) if (strcmp(name, XATTR_NAME_EVM) == 0)
return 1; /* Discard */ return 1; /* Discard */

5
security/security.c
View file

@ -2628,6 +2628,7 @@ EXPORT_SYMBOL(security_inode_copy_up);
/** /**
* security_inode_copy_up_xattr() - Filter xattrs in an overlayfs copy-up op * security_inode_copy_up_xattr() - Filter xattrs in an overlayfs copy-up op
* @src: union dentry of copy-up file
* @name: xattr name * @name: xattr name
* *
* Filter the xattrs being copied up when a unioned file is copied up from a * Filter the xattrs being copied up when a unioned file is copied up from a
@ -2638,7 +2639,7 @@ EXPORT_SYMBOL(security_inode_copy_up);
* if the security module does not know about attribute, or a negative * if the security module does not know about attribute, or a negative
* error code to abort the copy up. * error code to abort the copy up.
*/ */
int security_inode_copy_up_xattr(const char *name) int security_inode_copy_up_xattr(struct dentry *src, const char *name)
{ {
int rc; int rc;
@ -2647,7 +2648,7 @@ int security_inode_copy_up_xattr(const char *name)
* xattr), -EOPNOTSUPP if it does not know anything about the xattr or * xattr), -EOPNOTSUPP if it does not know anything about the xattr or
* any other error code in case of an error. * any other error code in case of an error.
*/ */
rc = call_int_hook(inode_copy_up_xattr, name); rc = call_int_hook(inode_copy_up_xattr, src, name);
if (rc != LSM_RET_DEFAULT(inode_copy_up_xattr)) if (rc != LSM_RET_DEFAULT(inode_copy_up_xattr))
return rc; return rc;

2
security/selinux/hooks.c
View file

@ -3530,7 +3530,7 @@ static int selinux_inode_copy_up(struct dentry *src, struct cred **new)
return 0; return 0;
} }
static int selinux_inode_copy_up_xattr(const char *name) static int selinux_inode_copy_up_xattr(struct dentry *dentry, const char *name)
{ {
/* The copy_up hook above sets the initial context on an inode, but we /* The copy_up hook above sets the initial context on an inode, but we
* don't then want to overwrite it by blindly copying all the lower * don't then want to overwrite it by blindly copying all the lower

2
security/smack/smack_lsm.c
View file

@ -4885,7 +4885,7 @@ static int smack_inode_copy_up(struct dentry *dentry, struct cred **new)
return 0; return 0;
} }
static int smack_inode_copy_up_xattr(const char *name) static int smack_inode_copy_up_xattr(struct dentry *src, const char *name)
{ {
/* /*
* Return 1 if this is the smack access Smack attribute. * Return 1 if this is the smack access Smack attribute.