From: Paul Moore <paul@paul-moore.com> stable inclusion from stable-v6.6.144 commit 41c5b269af8b1f0bffcab7766a793f294ae6764e category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/15316 CVE: CVE-2026-46054 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 6af36aeb147a06dea47c49859cd6ca5659aeb987 ] Stacked filesystems such as overlayfs do not currently provide the necessary mechanisms for LSMs to properly enforce access controls on the mmap() and mprotect() operations. In order to resolve this gap, a LSM security blob is being added to the backing_file struct and the following new LSM hooks are being created: security_backing_file_alloc() security_backing_file_free() security_mmap_backing_file() The first two hooks are to manage the lifecycle of the LSM security blob in the backing_file struct, while the third provides a new mmap() access control point for the underlying backing file. It is also expected that LSMs will likely want to update their security_file_mprotect() callback to address issues with their mprotect() controls, but that does not require a change to the security_file_mprotect() LSM hook. There are a three other small changes to support these new LSM hooks: * Pass the user file associated with a backing file down to alloc_empty_backing_file() so it can be included in the security_backing_file_alloc() hook. * Add getter and setter functions for the backing_file struct LSM blob as the backing_file struct remains private to fs/file_table.c. * Constify the file struct field in the LSM common_audit_data struct to better support LSMs that need to pass a const file struct pointer into the common LSM audit code. Thanks to Arnd Bergmann for identifying the missing EXPORT_SYMBOL_GPL() and supplying a fixup. Cc: stable@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org Cc: linux-unionfs@vger.kernel.org Cc: linux-erofs@lists.ozlabs.org Reviewed-by: Amir Goldstein <amir73il@gmail.com> Reviewed-by: Serge Hallyn <serge@hallyn.com> Reviewed-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Paul Moore <paul@paul-moore.com> [1. Mainline uses call_int_hook(FUNC, ...) with the default IRC baked into the macro. Linux 6.6.y uses call_int_hook(FUNC, IRC, ...) requiring an explicit default return value. 2. fs/backing-file.c does not exist in LTS Linux 6.6.y places backing_file_open() in fs/open.c and lacks a dedicated fs/backing-file.c. The backing_file_mmap() function and scoped_with_creds() do not exist in 6.6.y. Therefore the LTS patch calls security_mmap_backing_file() directly in ovl_mmap() in fs/overlayfs/file.c rather than modifying backing_file_mmap(). 3. Missing filesystems/modules Linux 6.6.y does not have backing_tmpfile_open(), fs/fuse/passthrough.c, or the erofs ishare mmap path that the mainline patch touches. These hunks are dropped in the 6.6 LTS backport. 4. Use macro backing_file to replace inline function to eliminate the const warning.] Signed-off-by: Cai Xinchen <caixinchen1@huawei.com> Signed-off-by: Sasha Levin <sashal@kernel.org> Conflicts: fs/file_table.c fs/internal.h fs/open.c fs/overlayfs/file.c include/linux/fs.h include/linux/lsm_hooks.h include/linux/lsm_audit.h security/security.c [fs/open.c: in ovl_open_realfile, we backport 924577e4f6ca ("ovl: Fix nested backing file paths"), do as mainline. fs/overlayfs/file.c: In 5.10 ovl_mmap, we should fput(realfile) in sescurity_mmap_backing_file failed. in the function backing_file_open, the commit def3ae83da02 ("fs: store real path instead of fake path in backing file f_path") is backport, do as mainline. Others are only context conflicts.] Signed-off-by: Cai Xinchen <caixinchen1@huawei.com> --- fs/file_table.c | 27 +++++++-- fs/internal.h | 3 +- fs/open.c | 5 +- fs/overlayfs/file.c | 12 +++- include/linux/fs.h | 15 ++++- include/linux/lsm_audit.h | 2 +- include/linux/lsm_hook_defs.h | 5 ++ include/linux/lsm_hooks.h | 1 + include/linux/security.h | 22 +++++++ security/security.c | 110 ++++++++++++++++++++++++++++++++++ 10 files changed, 191 insertions(+), 11 deletions(-) diff --git a/fs/file_table.c b/fs/file_table.c index 760fdc35899d..b4cacac62cce 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -77,6 +77,9 @@ static inline struct file *kmem_cache_zalloc_file(void) struct backing_file { struct file file; struct path user_path; +#ifdef CONFIG_SECURITY + void *security; +#endif }; #define backing_file(f) container_of(f, struct backing_file, file) @@ -104,8 +107,21 @@ static void file_free_rcu(struct rcu_head *head) kmem_cache_free(filp_cachep, GET_FILE_WRAP(f)); } +#ifdef CONFIG_SECURITY +void *backing_file_security(const struct file *f) +{ + return backing_file(f)->security; +} + +void backing_file_set_security(struct file *f, void *security) +{ + backing_file(f)->security = security; +} +#endif /* CONFIG_SECURITY */ + static inline void backing_file_free(struct backing_file *ff) { + security_backing_file_free(&ff->file); path_put(&ff->user_path); } @@ -254,10 +270,12 @@ struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred) return f; } -static int init_backing_file(struct backing_file *ff) +static int init_backing_file(struct backing_file *ff, + const struct file *user_file) { memset(&ff->user_path, 0, sizeof(ff->user_path)); - return 0; + backing_file_set_security(&ff->file, NULL); + return security_backing_file_alloc(&ff->file, user_file); } /* @@ -267,7 +285,8 @@ static int init_backing_file(struct backing_file *ff) * This is only for kernel internal use, and the allocate file must not be * installed into file tables or such. */ -struct file *alloc_empty_backing_file(int flags, const struct cred *cred) +struct file *alloc_empty_backing_file(int flags, const struct cred *cred, + const struct file *user_file) { struct backing_file *ff; int error; @@ -284,7 +303,7 @@ struct file *alloc_empty_backing_file(int flags, const struct cred *cred) /* The f_mode flags must be set before fput(). */ ff->file.f_mode |= FMODE_BACKING | FMODE_NOACCOUNT; - error = init_backing_file(ff); + error = init_backing_file(ff, user_file); if (unlikely(error)) { fput(&ff->file); return ERR_PTR(error); diff --git a/fs/internal.h b/fs/internal.h index 71a0a155ec8f..20974758595b 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -109,7 +109,8 @@ extern void chroot_fs_refs(const struct path *, const struct path *); */ struct file *alloc_empty_file(int flags, const struct cred *cred); struct file *alloc_empty_file_noaccount(int flags, const struct cred *cred); -struct file *alloc_empty_backing_file(int flags, const struct cred *cred); +struct file *alloc_empty_backing_file(int flags, const struct cred *cred, + const struct file *user_file); void backing_file_set_user_path(struct file *f, const struct path *path); static inline void file_put_write_access(struct file *file) diff --git a/fs/open.c b/fs/open.c index df3066e5d87a..44ffd83872d0 100644 --- a/fs/open.c +++ b/fs/open.c @@ -984,14 +984,15 @@ EXPORT_SYMBOL(dentry_open); * returned file into a container structure that also stores the stacked * file's path, which can be retrieved using backing_file_user_path(). */ -struct file *backing_file_open(const struct path *user_path, int flags, +struct file *backing_file_open(const struct file *user_file, int flags, const struct path *real_path, const struct cred *cred) { + const struct path *user_path = &user_file->f_path; struct file *f; int error; - f = alloc_empty_backing_file(flags, cred); + f = alloc_empty_backing_file(flags, cred, user_file); if (IS_ERR(f)) return f; diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index f0e0d7904150..02427e6fdfb0 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -58,8 +58,8 @@ static struct file *ovl_open_realfile(const struct file *file, if (!inode_owner_or_capable(realinode)) flags &= ~O_NOATIME; - realfile = backing_file_open(file_user_path((struct file *) file), - flags, realpath, current_cred()); + realfile = backing_file_open(file, flags, realpath, + current_cred()); } revert_creds(old_cred); @@ -491,6 +491,7 @@ static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync) static int ovl_mmap(struct file *file, struct vm_area_struct *vma) { + struct file *user_file = vma->vm_file; struct file *realfile = file->private_data; const struct cred *old_cred; int ret; @@ -504,6 +505,13 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma) vma->vm_file = get_file(realfile); old_cred = ovl_override_creds(file_inode(file)->i_sb); + ret = security_mmap_backing_file(vma, realfile, user_file); + if (ret) { + revert_creds(old_cred); + fput(realfile); + return ret; + } + ret = call_mmap(vma->vm_file, vma); revert_creds(old_cred); diff --git a/include/linux/fs.h b/include/linux/fs.h index d90265b6c61d..8ca24d2f79f9 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2720,11 +2720,24 @@ struct file *dentry_open(const struct path *path, int flags, const struct cred *creds); struct file *dentry_create(const struct path *path, int flags, umode_t mode, const struct cred *cred); -struct file *backing_file_open(const struct path *user_path, int flags, +struct file *backing_file_open(const struct file *user_file, int flags, const struct path *real_path, const struct cred *cred); struct path *backing_file_user_path(const struct file *f); +#ifdef CONFIG_SECURITY +void *backing_file_security(const struct file *f); +void backing_file_set_security(struct file *f, void *security); +#else +static inline void *backing_file_security(const struct file *f) +{ + return NULL; +} +static inline void backing_file_set_security(struct file *f, void *security) +{ +} +#endif /* CONFIG_SECURITY */ + /* * file_user_path - get the path to display for memory mapped file * diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h index 28f23b341c1c..8b42e110cb26 100644 --- a/include/linux/lsm_audit.h +++ b/include/linux/lsm_audit.h @@ -92,7 +92,7 @@ struct common_audit_data { #endif char *kmod_name; struct lsm_ioctlop_audit *op; - struct file *file; + const struct file *file; struct lsm_ibpkey_audit *ibpkey; struct lsm_ibendport_audit *ibendport; int reason; diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index eb15ba8b2c7d..0bb58214b130 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -157,6 +157,9 @@ LSM_HOOK(int, 0, kernfs_init_security, struct kernfs_node *kn_dir, LSM_HOOK(int, 0, file_permission, struct file *file, int mask) LSM_HOOK(int, 0, file_alloc_security, struct file *file) LSM_HOOK(void, LSM_RET_VOID, file_free_security, struct file *file) +LSM_HOOK(int, 0, backing_file_alloc, struct file *backing_file, + const struct file *user_file) +LSM_HOOK(void, LSM_RET_VOID, backing_file_free, struct file *backing_file) LSM_HOOK(int, 0, file_ioctl, struct file *file, unsigned int cmd, unsigned long arg) LSM_HOOK(int, 0, file_ioctl_compat, struct file *file, unsigned int cmd, @@ -164,6 +167,8 @@ LSM_HOOK(int, 0, file_ioctl_compat, struct file *file, unsigned int cmd, LSM_HOOK(int, 0, mmap_addr, unsigned long addr) LSM_HOOK(int, 0, mmap_file, struct file *file, unsigned long reqprot, unsigned long prot, unsigned long flags) +LSM_HOOK(int, 0, mmap_backing_file, struct vm_area_struct *vma, + struct file *backing_file, struct file *user_file) LSM_HOOK(int, 0, file_mprotect, struct vm_area_struct *vma, unsigned long reqprot, unsigned long prot) LSM_HOOK(int, 0, file_lock, struct file *file, unsigned int cmd) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 21b3c43cd05a..8cc442b95d5a 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -1566,6 +1566,7 @@ struct security_hook_list { struct lsm_blob_sizes { int lbs_cred; int lbs_file; + int lbs_backing_file; int lbs_inode; int lbs_superblock; int lbs_ipc; diff --git a/include/linux/security.h b/include/linux/security.h index b9cd823992f5..3d80ee8e8eae 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -370,11 +370,17 @@ int security_kernfs_init_security(struct kernfs_node *kn_dir, int security_file_permission(struct file *file, int mask); int security_file_alloc(struct file *file); void security_file_free(struct file *file); +int security_backing_file_alloc(struct file *backing_file, + const struct file *user_file); +void security_backing_file_free(struct file *backing_file); int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg); int security_file_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg); int security_mmap_file(struct file *file, unsigned long prot, unsigned long flags); +int security_mmap_backing_file(struct vm_area_struct *vma, + struct file *backing_file, + struct file *user_file); int security_mmap_addr(unsigned long addr); int security_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot, unsigned long prot); @@ -927,6 +933,15 @@ static inline int security_file_alloc(struct file *file) static inline void security_file_free(struct file *file) { } +static inline int security_backing_file_alloc(struct file *backing_file, + const struct file *user_file) +{ + return 0; +} + +static inline void security_backing_file_free(struct file *backing_file) +{ } + static inline int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { @@ -946,6 +961,13 @@ static inline int security_mmap_file(struct file *file, unsigned long prot, return 0; } +static inline int security_mmap_backing_file(struct vm_area_struct *vma, + struct file *backing_file, + struct file *user_file) +{ + return 0; +} + static inline int security_mmap_addr(unsigned long addr) { return cap_mmap_addr(addr); diff --git a/security/security.c b/security/security.c index a86aa7f34ce2..a3370f188cb7 100644 --- a/security/security.c +++ b/security/security.c @@ -76,6 +76,7 @@ struct security_hook_heads security_hook_heads __lsm_ro_after_init; static BLOCKING_NOTIFIER_HEAD(blocking_lsm_notifier_chain); static struct kmem_cache *lsm_file_cache; +static struct kmem_cache *lsm_backing_file_cache; static struct kmem_cache *lsm_inode_cache; char *lsm_names; @@ -197,6 +198,8 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed) lsm_set_blob_size(&needed->lbs_cred, &blob_sizes.lbs_cred); lsm_set_blob_size(&needed->lbs_file, &blob_sizes.lbs_file); + lsm_set_blob_size(&needed->lbs_backing_file, + &blob_sizes.lbs_backing_file); /* * The inode blob gets an rcu_head in addition to * what the modules might need. @@ -339,6 +342,7 @@ static void __init ordered_lsm_init(void) init_debug("cred blob size = %d\n", blob_sizes.lbs_cred); init_debug("file blob size = %d\n", blob_sizes.lbs_file); + init_debug("backing_file blob size = %d\n", blob_sizes.lbs_backing_file); init_debug("inode blob size = %d\n", blob_sizes.lbs_inode); init_debug("ipc blob size = %d\n", blob_sizes.lbs_ipc); init_debug("msg_msg blob size = %d\n", blob_sizes.lbs_msg_msg); @@ -352,6 +356,11 @@ static void __init ordered_lsm_init(void) lsm_file_cache = kmem_cache_create("lsm_file_cache", blob_sizes.lbs_file, 0, SLAB_PANIC, NULL); + if (blob_sizes.lbs_backing_file) + lsm_backing_file_cache = kmem_cache_create( + "lsm_backing_file_cache", + blob_sizes.lbs_backing_file, + 0, SLAB_PANIC, NULL); if (blob_sizes.lbs_inode) lsm_inode_cache = kmem_cache_create("lsm_inode_cache", blob_sizes.lbs_inode, 0, @@ -577,6 +586,30 @@ static int lsm_file_alloc(struct file *file) return 0; } +/** + * lsm_backing_file_alloc - allocate a composite backing file blob + * @backing_file: the backing file + * + * Allocate the backing file blob for all the modules. + * + * Returns 0, or -ENOMEM if memory can't be allocated. + */ +static int lsm_backing_file_alloc(struct file *backing_file) +{ + void *blob; + + if (!lsm_backing_file_cache) { + backing_file_set_security(backing_file, NULL); + return 0; + } + + blob = kmem_cache_zalloc(lsm_backing_file_cache, GFP_KERNEL); + backing_file_set_security(backing_file, blob); + if (!blob) + return -ENOMEM; + return 0; +} + /** * lsm_inode_alloc - allocate a composite inode blob * @inode: the inode that needs a blob @@ -1545,6 +1578,57 @@ void security_file_free(struct file *file) } } +/** + * security_backing_file_alloc() - Allocate and setup a backing file blob + * @backing_file: the backing file + * @user_file: the associated user visible file + * + * Allocate a backing file LSM blob and perform any necessary initialization of + * the LSM blob. There will be some operations where the LSM will not have + * access to @user_file after this point, so any important state associated + * with @user_file that is important to the LSM should be captured in the + * backing file's LSM blob. + * + * LSM's should avoid taking a reference to @user_file in this hook as it will + * result in problems later when the system attempts to drop/put the file + * references due to a circular dependency. + * + * Return: Return 0 if the hook is successful, negative values otherwise. + */ +int security_backing_file_alloc(struct file *backing_file, + const struct file *user_file) +{ + int rc; + + rc = lsm_backing_file_alloc(backing_file); + if (rc) + return rc; + rc = call_int_hook(backing_file_alloc, 0, backing_file, user_file); + if (unlikely(rc)) + security_backing_file_free(backing_file); + + return rc; +} + +/** + * security_backing_file_free() - Free a backing file blob + * @backing_file: the backing file + * + * Free any LSM state associate with a backing file's LSM blob, including the + * blob itself. + */ +void security_backing_file_free(struct file *backing_file) +{ + void *blob = backing_file_security(backing_file); + + call_void_hook(backing_file_free, backing_file); + + if (blob) { + backing_file_set_security(backing_file, NULL); + kmem_cache_free(lsm_backing_file_cache, blob); + } +} + int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { return call_int_hook(file_ioctl, 0, file, cmd, arg); @@ -1614,6 +1698,32 @@ int security_mmap_file(struct file *file, unsigned long prot, return ima_file_mmap(file, prot, prot_adj, flags); } +/** + * security_mmap_backing_file - Check if mmap'ing a backing file is allowed + * @vma: the vm_area_struct for the mmap'd region + * @backing_file: the backing file being mmap'd + * @user_file: the user file being mmap'd + * + * Check permissions for a mmap operation on a stacked filesystem. This hook + * is called after the security_mmap_file() and is responsible for authorizing + * the mmap on @backing_file. It is important to note that the mmap operation + * on @user_file has already been authorized and the @vma->vm_file has been + * set to @backing_file. + * + * Return: Returns 0 if permission is granted. + */ +int security_mmap_backing_file(struct vm_area_struct *vma, + struct file *backing_file, + struct file *user_file) +{ + /* recommended by the stackable filesystem devs */ + if (WARN_ON_ONCE(!(backing_file->f_mode & FMODE_BACKING))) + return -EIO; + + return call_int_hook(mmap_backing_file, 0, vma, backing_file, user_file); +} +EXPORT_SYMBOL_GPL(security_mmap_backing_file); + int security_mmap_addr(unsigned long addr) { return call_int_hook(mmap_addr, 0, addr); -- 2.18.0.huawei.25