diff options
Diffstat (limited to 'security/selinux/hooks.c')
| -rw-r--r-- | security/selinux/hooks.c | 150 |
1 files changed, 133 insertions, 17 deletions
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index e5e17f100aae..3f4a6ddee322 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -1674,26 +1674,32 @@ static int cred_has_capability(const struct cred *cred, return rc; } -/* Check whether a task has a particular permission to an inode. - The 'adp' parameter is optional and allows other audit - data to be passed (e.g. the dentry). */ -static int inode_has_perm(const struct cred *cred, - struct inode *inode, - u32 perms, - struct common_audit_data *adp) +/* + * Check whether a SID has a particular permission to an inode. The 'adp' + * parameter is optional and allows other audit data to be passed (e.g. the + * dentry). + */ +static int inode_sid_has_perm(u32 sid, struct inode *inode, u32 perms, + struct common_audit_data *adp) { struct inode_security_struct *isec; - u32 sid; if (unlikely(IS_PRIVATE(inode))) return 0; - sid = cred_sid(cred); isec = selinux_inode(inode); return avc_has_perm(sid, isec->sid, isec->sclass, perms, adp); } +static int inode_has_perm(const struct cred *cred, + struct inode *inode, + u32 perms, + struct common_audit_data *adp) +{ + return inode_sid_has_perm(cred_sid(cred), inode, perms, adp); +} + /* Same as inode_has_perm, but pass explicit audit data containing the dentry to help the auditing code to more easily generate the pathname if needed. */ @@ -3843,17 +3849,74 @@ static int selinux_file_alloc_security(struct file *file) return 0; } +static inline u32 selinux_file_user_sid(const struct file *file) +{ + if (unlikely(file->f_mode & FMODE_BACKING)) + return selinux_backing_file(file)->uf_sid; + return selinux_file(file)->sid; +} + static int selinux_backing_file_alloc(struct file *backing_file, const struct file *user_file) { struct backing_file_security_struct *bfsec; + const struct backing_file_security_struct *ubfsec; + struct backing_file_security_layer *layer; + u32 i; bfsec = selinux_backing_file(backing_file); - bfsec->uf_sid = selinux_file(user_file)->sid; + bfsec->uf_sid = selinux_file_user_sid(user_file); + if (!(user_file->f_mode & FMODE_BACKING)) + return 0; + + ubfsec = selinux_backing_file(user_file); + /* a wrapped count would make kmalloc_array() return ZERO_SIZE_PTR */ + if (unlikely(ubfsec->layer_count == U32_MAX)) + return -EOVERFLOW; + + /* + * The final VMA only retains the lowest backing file, so record the + * whole chain here rather than in the mmap hook, where concurrent + * mappings would have to be serialized. Size it dynamically: erofs + * inode sharing adds a backing file without bumping s_stack_depth. + */ + bfsec->layers = kmalloc_array(ubfsec->layer_count + 1, + sizeof(*bfsec->layers), GFP_KERNEL); + if (!bfsec->layers) + return -ENOMEM; + + for (i = 0; i < ubfsec->layer_count; i++) { + layer = &bfsec->layers[i]; + *layer = ubfsec->layers[i]; + path_get(&layer->path); + } + + /* f_path, not file_user_path(): this layer, not the top-level file */ + layer = &bfsec->layers[i]; + layer->path = user_file->f_path; + layer->mounter_sid = cred_sid(user_file->f_cred); + layer->fd_sid = selinux_file(user_file)->sid; + path_get(&layer->path); + bfsec->layer_count = ubfsec->layer_count + 1; return 0; } +static void selinux_backing_file_free(struct file *backing_file) +{ + struct backing_file_security_struct *bfsec; + + /* security_backing_file_free() may be called twice after an error */ + if (!backing_file_security(backing_file)) + return; + + bfsec = selinux_backing_file(backing_file); + while (bfsec->layer_count) + path_put(&bfsec->layers[--bfsec->layer_count].path); + kfree(bfsec->layers); + bfsec->layers = NULL; +} + /* * Check whether a task has the ioctl permission and cmd * operation to an inode. @@ -3971,6 +4034,53 @@ static int selinux_file_ioctl_compat(struct file *file, unsigned int cmd, static int default_noexec __ro_after_init; +static u32 file_map_prot_to_av(unsigned long prot, bool shared) +{ + u32 av = FILE__READ; + + if (shared && (prot & PROT_WRITE)) + av |= FILE__WRITE; + if (prot & PROT_EXEC) + av |= FILE__EXECUTE; + + return av; +} + +static int backing_mounters_has_perm(const struct file *file, u32 av) +{ + const struct backing_file_security_struct *bfsec; + const struct backing_file_security_layer *layer; + struct common_audit_data ad; + struct inode *inode; + u32 i; + int rc; + + if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING))) + return -EIO; + + bfsec = selinux_backing_file(file); + for (i = 0; i < bfsec->layer_count; i++) { + layer = &bfsec->layers[i]; + inode = d_inode(layer->path.dentry); + + ad.type = LSM_AUDIT_DATA_PATH; + ad.u.path = layer->path; + + if (layer->mounter_sid != layer->fd_sid) { + rc = avc_has_perm(layer->mounter_sid, layer->fd_sid, + SECCLASS_FD, FD__USE, &ad); + if (rc) + return rc; + } + + rc = inode_sid_has_perm(layer->mounter_sid, inode, av, &ad); + if (rc) + return rc; + } + + return 0; +} + static int __file_map_prot_check(const struct file *file, unsigned long prot, bool shared, bool mounter_check, bool bf_user_file) @@ -4004,14 +4114,10 @@ static int __file_map_prot_check(const struct file *file, unsigned long prot, if (file) { const struct cred *cred = mounter_check ? file->f_cred : current_cred(); - /* "read" always possible, "write" only if shared */ - u32 av = FILE__READ; - if (shared && prot_write) - av |= FILE__WRITE; - if (prot_exec) - av |= FILE__EXECUTE; - return __file_has_perm(cred, file, av, bf_user_file); + return __file_has_perm(cred, file, + file_map_prot_to_av(prot, shared), + bf_user_file); } return 0; @@ -4106,6 +4212,7 @@ static int selinux_file_mprotect(struct vm_area_struct *vma, int rc; const struct cred *cred = current_cred(); u32 sid = cred_sid(cred); + u32 av; const struct file *file = vma->vm_file; bool backing_file; bool shared = vma->vm_flags & VM_SHARED; @@ -4149,6 +4256,10 @@ static int selinux_file_mprotect(struct vm_area_struct *vma, if (rc) return rc; if (backing_file) { + rc = backing_mounters_has_perm(file, + FILE__EXECMOD); + if (rc) + return rc; rc = file_has_perm(file->f_cred, file, FILE__EXECMOD); if (rc) @@ -4161,6 +4272,10 @@ static int selinux_file_mprotect(struct vm_area_struct *vma, if (rc) return rc; if (backing_file) { + av = file_map_prot_to_av(prot, shared); + rc = backing_mounters_has_perm(file, av); + if (rc) + return rc; rc = file_map_prot_check(file, prot, shared, true); if (rc) return rc; @@ -7619,6 +7734,7 @@ static struct security_hook_list selinux_hooks[] __ro_after_init = { LSM_HOOK_INIT(file_permission, selinux_file_permission), LSM_HOOK_INIT(file_alloc_security, selinux_file_alloc_security), LSM_HOOK_INIT(backing_file_alloc, selinux_backing_file_alloc), + LSM_HOOK_INIT(backing_file_free, selinux_backing_file_free), LSM_HOOK_INIT(file_ioctl, selinux_file_ioctl), LSM_HOOK_INIT(file_ioctl_compat, selinux_file_ioctl_compat), LSM_HOOK_INIT(mmap_file, selinux_mmap_file), |