From 4f0b9194bc119a9850a99e5e824808e2f468c348 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 3 Nov 2023 06:47:51 -0400 Subject: fs: Rename anon_inode_getfile_secure() and anon_inode_getfd_secure() The call to the inode_init_security_anon() LSM hook is not the sole reason to use anon_inode_getfile_secure() or anon_inode_getfd_secure(). For example, the functions also allow one to create a file with non-zero size, without needing a full-blown filesystem. In this case, you don't need a "secure" version, just unique inodes; the current name of the functions is confusing and does not explain well the difference with the more "standard" anon_inode_getfile() and anon_inode_getfd(). Of course, there is another side of the coin; neither io_uring nor userfaultfd strictly speaking need distinct inodes, and it is not that clear anymore that anon_inode_create_get{file,fd}() allow the LSM to intercept and block the inode's creation. If one was so inclined, anon_inode_getfile_secure() and anon_inode_getfd_secure() could be kept, using the shared inode or a new one depending on CONFIG_SECURITY. However, this is probably overkill, and potentially a cause of bugs in different configurations. Therefore, just add a comment to io_uring and userfaultfd explaining the choice of the function. While at it, remove the export for what is now anon_inode_create_getfd(). There is no in-tree module that uses it, and the old name is gone anyway. If anybody actually needs the symbol, they can ask or they can just use anon_inode_create_getfile(), which will be exported very soon for use in KVM. Suggested-by: Christian Brauner Reviewed-by: Christian Brauner Signed-off-by: Paolo Bonzini --- fs/anon_inodes.c | 50 ++++++++++++++++++++++++++++++--------------- fs/userfaultfd.c | 5 +++-- include/linux/anon_inodes.h | 4 ++-- io_uring/io_uring.c | 3 ++- 4 files changed, 40 insertions(+), 22 deletions(-) diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c index 24192a7667ed..42b02dc36474 100644 --- a/fs/anon_inodes.c +++ b/fs/anon_inodes.c @@ -79,7 +79,7 @@ static struct file *__anon_inode_getfile(const char *name, const struct file_operations *fops, void *priv, int flags, const struct inode *context_inode, - bool secure) + bool make_inode) { struct inode *inode; struct file *file; @@ -87,7 +87,7 @@ static struct file *__anon_inode_getfile(const char *name, if (fops->owner && !try_module_get(fops->owner)) return ERR_PTR(-ENOENT); - if (secure) { + if (make_inode) { inode = anon_inode_make_secure_inode(name, context_inode); if (IS_ERR(inode)) { file = ERR_CAST(inode); @@ -149,13 +149,10 @@ struct file *anon_inode_getfile(const char *name, EXPORT_SYMBOL_GPL(anon_inode_getfile); /** - * anon_inode_getfile_secure - Like anon_inode_getfile(), but creates a new + * anon_inode_create_getfile - Like anon_inode_getfile(), but creates a new * !S_PRIVATE anon inode rather than reuse the * singleton anon inode and calls the - * inode_init_security_anon() LSM hook. This - * allows for both the inode to have its own - * security context and for the LSM to enforce - * policy on the inode's creation. + * inode_init_security_anon() LSM hook. * * @name: [in] name of the "class" of the new file * @fops: [in] file operations for the new file @@ -164,11 +161,21 @@ EXPORT_SYMBOL_GPL(anon_inode_getfile); * @context_inode: * [in] the logical relationship with the new inode (optional) * + * Create a new anonymous inode and file pair. This can be done for two + * reasons: + * + * - for the inode to have its own security context, so that LSMs can enforce + * policy on the inode's creation; + * + * - if the caller needs a unique inode, for example in order to customize + * the size returned by fstat() + * * The LSM may use @context_inode in inode_init_security_anon(), but a - * reference to it is not held. Returns the newly created file* or an error - * pointer. See the anon_inode_getfile() documentation for more information. + * reference to it is not held. + * + * Returns the newly created file* or an error pointer. */ -struct file *anon_inode_getfile_secure(const char *name, +struct file *anon_inode_create_getfile(const char *name, const struct file_operations *fops, void *priv, int flags, const struct inode *context_inode) @@ -181,7 +188,7 @@ static int __anon_inode_getfd(const char *name, const struct file_operations *fops, void *priv, int flags, const struct inode *context_inode, - bool secure) + bool make_inode) { int error, fd; struct file *file; @@ -192,7 +199,7 @@ static int __anon_inode_getfd(const char *name, fd = error; file = __anon_inode_getfile(name, fops, priv, flags, context_inode, - secure); + make_inode); if (IS_ERR(file)) { error = PTR_ERR(file); goto err_put_unused_fd; @@ -231,10 +238,9 @@ int anon_inode_getfd(const char *name, const struct file_operations *fops, EXPORT_SYMBOL_GPL(anon_inode_getfd); /** - * anon_inode_getfd_secure - Like anon_inode_getfd(), but creates a new + * anon_inode_create_getfd - Like anon_inode_getfd(), but creates a new * !S_PRIVATE anon inode rather than reuse the singleton anon inode, and calls - * the inode_init_security_anon() LSM hook. This allows the inode to have its - * own security context and for a LSM to reject creation of the inode. + * the inode_init_security_anon() LSM hook. * * @name: [in] name of the "class" of the new file * @fops: [in] file operations for the new file @@ -243,16 +249,26 @@ EXPORT_SYMBOL_GPL(anon_inode_getfd); * @context_inode: * [in] the logical relationship with the new inode (optional) * + * Create a new anonymous inode and file pair. This can be done for two + * reasons: + * + * - for the inode to have its own security context, so that LSMs can enforce + * policy on the inode's creation; + * + * - if the caller needs a unique inode, for example in order to customize + * the size returned by fstat() + * * The LSM may use @context_inode in inode_init_security_anon(), but a * reference to it is not held. + * + * Returns a newly created file descriptor or an error code. */ -int anon_inode_getfd_secure(const char *name, const struct file_operations *fops, +int anon_inode_create_getfd(const char *name, const struct file_operations *fops, void *priv, int flags, const struct inode *context_inode) { return __anon_inode_getfd(name, fops, priv, flags, context_inode, true); } -EXPORT_SYMBOL_GPL(anon_inode_getfd_secure); static int __init anon_inode_init(void) { diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 56eaae9dac1a..7a1cf8bab5eb 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1033,7 +1033,7 @@ static int resolve_userfault_fork(struct userfaultfd_ctx *new, { int fd; - fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, new, + fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, new, O_RDONLY | (new->flags & UFFD_SHARED_FCNTL_FLAGS), inode); if (fd < 0) return fd; @@ -2205,7 +2205,8 @@ static int new_userfaultfd(int flags) /* prevent the mm struct to be freed */ mmgrab(ctx->mm); - fd = anon_inode_getfd_secure("[userfaultfd]", &userfaultfd_fops, ctx, + /* Create a new inode so that the LSM can block the creation. */ + fd = anon_inode_create_getfd("[userfaultfd]", &userfaultfd_fops, ctx, O_RDONLY | (flags & UFFD_SHARED_FCNTL_FLAGS), NULL); if (fd < 0) { mmdrop(ctx->mm); diff --git a/include/linux/anon_inodes.h b/include/linux/anon_inodes.h index 5deaddbd7927..93a5f16d03f3 100644 --- a/include/linux/anon_inodes.h +++ b/include/linux/anon_inodes.h @@ -15,13 +15,13 @@ struct inode; struct file *anon_inode_getfile(const char *name, const struct file_operations *fops, void *priv, int flags); -struct file *anon_inode_getfile_secure(const char *name, +struct file *anon_inode_create_getfile(const char *name, const struct file_operations *fops, void *priv, int flags, const struct inode *context_inode); int anon_inode_getfd(const char *name, const struct file_operations *fops, void *priv, int flags); -int anon_inode_getfd_secure(const char *name, +int anon_inode_create_getfd(const char *name, const struct file_operations *fops, void *priv, int flags, const struct inode *context_inode); diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 8d1bc6cdfe71..22b98f47bb28 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -3835,7 +3835,8 @@ static struct file *io_uring_get_file(struct io_ring_ctx *ctx) return ERR_PTR(ret); #endif - file = anon_inode_getfile_secure("[io_uring]", &io_uring_fops, ctx, + /* Create a new inode so that the LSM can block the creation. */ + file = anon_inode_create_getfile("[io_uring]", &io_uring_fops, ctx, O_RDWR | O_CLOEXEC, NULL); #if defined(CONFIG_UNIX) if (IS_ERR(file)) { -- cgit