Introduct new xattr name prefix security.bpf., and enable reading these xattrs from bpf kfuncs bpf_get_[file|dentry]_xattr(). As we are on it, correct the comments for return value of bpf_get_[file|dentry]_xattr(), i.e. return length the xattr value on success. Signed-off-by: Song Liu <song@xxxxxxxxxx> Acked-by: Christian Brauner <brauner@xxxxxxxxxx> Reviewed-by: Jan Kara <jack@xxxxxxx> --- fs/bpf_fs_kfuncs.c | 19 ++++++++++++++----- include/uapi/linux/xattr.h | 4 ++++ 2 files changed, 18 insertions(+), 5 deletions(-) diff --git a/fs/bpf_fs_kfuncs.c b/fs/bpf_fs_kfuncs.c index 3fe9f59ef867..8a65184c8c2c 100644 --- a/fs/bpf_fs_kfuncs.c +++ b/fs/bpf_fs_kfuncs.c @@ -93,6 +93,11 @@ __bpf_kfunc int bpf_path_d_path(struct path *path, char *buf, size_t buf__sz) return len; } +static bool match_security_bpf_prefix(const char *name__str) +{ + return !strncmp(name__str, XATTR_NAME_BPF_LSM, XATTR_NAME_BPF_LSM_LEN); +} + /** * bpf_get_dentry_xattr - get xattr of a dentry * @dentry: dentry to get xattr from @@ -101,9 +106,10 @@ __bpf_kfunc int bpf_path_d_path(struct path *path, char *buf, size_t buf__sz) * * Get xattr *name__str* of *dentry* and store the output in *value_ptr*. * - * For security reasons, only *name__str* with prefix "user." is allowed. + * For security reasons, only *name__str* with prefix "user." or + * "security.bpf." is allowed. * - * Return: 0 on success, a negative value on error. + * Return: length of the xattr value on success, a negative value on error. */ __bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *name__str, struct bpf_dynptr *value_p) @@ -117,7 +123,9 @@ __bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *name__st if (WARN_ON(!inode)) return -EINVAL; - if (strncmp(name__str, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) + /* Allow reading xattr with user. and security.bpf. prefix */ + if (strncmp(name__str, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN) && + !match_security_bpf_prefix(name__str)) return -EPERM; value_len = __bpf_dynptr_size(value_ptr); @@ -139,9 +147,10 @@ __bpf_kfunc int bpf_get_dentry_xattr(struct dentry *dentry, const char *name__st * * Get xattr *name__str* of *file* and store the output in *value_ptr*. * - * For security reasons, only *name__str* with prefix "user." is allowed. + * For security reasons, only *name__str* with prefix "user." or + * "security.bpf." is allowed. * - * Return: 0 on success, a negative value on error. + * Return: length of the xattr value on success, a negative value on error. */ __bpf_kfunc int bpf_get_file_xattr(struct file *file, const char *name__str, struct bpf_dynptr *value_p) diff --git a/include/uapi/linux/xattr.h b/include/uapi/linux/xattr.h index 9854f9cff3c6..c7c85bb504ba 100644 --- a/include/uapi/linux/xattr.h +++ b/include/uapi/linux/xattr.h @@ -83,6 +83,10 @@ struct xattr_args { #define XATTR_CAPS_SUFFIX "capability" #define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX +#define XATTR_BPF_LSM_SUFFIX "bpf." +#define XATTR_NAME_BPF_LSM (XATTR_SECURITY_PREFIX XATTR_BPF_LSM_SUFFIX) +#define XATTR_NAME_BPF_LSM_LEN (sizeof(XATTR_NAME_BPF_LSM) - 1) + #define XATTR_POSIX_ACL_ACCESS "posix_acl_access" #define XATTR_NAME_POSIX_ACL_ACCESS XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_ACCESS #define XATTR_POSIX_ACL_DEFAULT "posix_acl_default" -- 2.43.5