From 56851bc9b9f072dd738f25ed29c0d5abe9f2908b Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 29 Sep 2022 10:47:36 +0200 Subject: internal: add may_write_xattr() Split out the generic checks whether an inode allows writing xattrs. Since security.* and system.* xattrs don't have any restrictions and we're going to split out posix acls into a dedicated api we will use this helper to check whether we can write posix acls. Signed-off-by: Christian Brauner (Microsoft) --- fs/internal.h | 1 + 1 file changed, 1 insertion(+) (limited to 'fs/internal.h') diff --git a/fs/internal.h b/fs/internal.h index 6f0386b34fae..aa5f240496d9 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -232,5 +232,6 @@ ssize_t do_getxattr(struct user_namespace *mnt_userns, int setxattr_copy(const char __user *name, struct xattr_ctx *ctx); int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry, struct xattr_ctx *ctx); +int may_write_xattr(struct user_namespace *mnt_userns, struct inode *inode); ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos); -- cgit v1.2.3 From 318e66856ddec05384f32d60b5598128289f4e7b Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Thu, 22 Sep 2022 17:17:22 +0200 Subject: xattr: use posix acl api In previous patches we built a new posix api solely around get and set inode operations. Now that we have all the pieces in place we can switch the system calls and the vfs over to only rely on this api when interacting with posix acls. This finally removes all type unsafety and type conversion issues explained in detail in [1] that we aim to get rid of. With the new posix acl api we immediately translate into an appropriate kernel internal struct posix_acl format both when getting and setting posix acls. This is a stark contrast to before were we hacked unsafe raw values into the uapi struct that was stored in a void pointer relying and having filesystems and security modules hack around in the uapi struct as well. Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1] Signed-off-by: Christian Brauner (Microsoft) --- fs/internal.h | 20 ++++++++++++++++++++ fs/posix_acl.c | 37 +++++++++++++++++++++++++++++++++++++ fs/xattr.c | 31 ++++++++++++++++++++----------- include/linux/posix_acl_xattr.h | 10 ++++++++-- 4 files changed, 85 insertions(+), 13 deletions(-) (limited to 'fs/internal.h') diff --git a/fs/internal.h b/fs/internal.h index aa5f240496d9..e377eb7bbe7f 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -234,4 +234,24 @@ int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry, struct xattr_ctx *ctx); int may_write_xattr(struct user_namespace *mnt_userns, struct inode *inode); +#ifdef CONFIG_FS_POSIX_ACL +int do_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry, + const char *acl_name, const void *kvalue, size_t size); +ssize_t do_get_acl(struct user_namespace *mnt_userns, struct dentry *dentry, + const char *acl_name, void *kvalue, size_t size); +#else +static inline int do_set_acl(struct user_namespace *mnt_userns, + struct dentry *dentry, const char *acl_name, + const void *kvalue, size_t size) +{ + return -EOPNOTSUPP; +} +static inline ssize_t do_get_acl(struct user_namespace *mnt_userns, + struct dentry *dentry, const char *acl_name, + void *kvalue, size_t size) +{ + return -EOPNOTSUPP; +} +#endif + ssize_t __kernel_write_iter(struct file *file, struct iov_iter *from, loff_t *pos); diff --git a/fs/posix_acl.c b/fs/posix_acl.c index 3a141082b24c..14b87653b797 100644 --- a/fs/posix_acl.c +++ b/fs/posix_acl.c @@ -1544,3 +1544,40 @@ out_inode_unlock: return error; } EXPORT_SYMBOL_GPL(vfs_remove_acl); + +int do_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry, + const char *acl_name, const void *kvalue, size_t size) +{ + int error; + struct posix_acl *acl = NULL; + + if (size) { + /* + * Note that posix_acl_from_xattr() uses GFP_NOFS when it + * probably doesn't need to here. + */ + acl = posix_acl_from_xattr(current_user_ns(), kvalue, size); + if (IS_ERR(acl)) + return PTR_ERR(acl); + } + + error = vfs_set_acl(mnt_userns, dentry, acl_name, acl); + posix_acl_release(acl); + return error; +} + +ssize_t do_get_acl(struct user_namespace *mnt_userns, struct dentry *dentry, + const char *acl_name, void *kvalue, size_t size) +{ + ssize_t error; + struct posix_acl *acl; + + acl = vfs_get_acl(mnt_userns, dentry, acl_name); + if (IS_ERR(acl)) + return PTR_ERR(acl); + + error = vfs_posix_acl_to_xattr(mnt_userns, d_inode(dentry), + acl, kvalue, size); + posix_acl_release(acl); + return error; +} diff --git a/fs/xattr.c b/fs/xattr.c index 9ed9eea4d1b9..77db5aa26d13 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -189,6 +189,9 @@ __vfs_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry, { const struct xattr_handler *handler; + if (is_posix_acl_xattr(name)) + return -EOPNOTSUPP; + handler = xattr_resolve_name(inode, &name); if (IS_ERR(handler)) return PTR_ERR(handler); @@ -410,6 +413,9 @@ __vfs_getxattr(struct dentry *dentry, struct inode *inode, const char *name, { const struct xattr_handler *handler; + if (is_posix_acl_xattr(name)) + return -EOPNOTSUPP; + handler = xattr_resolve_name(inode, &name); if (IS_ERR(handler)) return PTR_ERR(handler); @@ -482,6 +488,9 @@ __vfs_removexattr(struct user_namespace *mnt_userns, struct dentry *dentry, struct inode *inode = d_inode(dentry); const struct xattr_handler *handler; + if (is_posix_acl_xattr(name)) + return -EOPNOTSUPP; + handler = xattr_resolve_name(inode, &name); if (IS_ERR(handler)) return PTR_ERR(handler); @@ -591,17 +600,13 @@ int setxattr_copy(const char __user *name, struct xattr_ctx *ctx) return error; } -static void setxattr_convert(struct user_namespace *mnt_userns, - struct dentry *d, struct xattr_ctx *ctx) -{ - if (ctx->size && is_posix_acl_xattr(ctx->kname->name)) - posix_acl_fix_xattr_from_user(ctx->kvalue, ctx->size); -} - int do_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry, struct xattr_ctx *ctx) { - setxattr_convert(mnt_userns, dentry, ctx); + if (is_posix_acl_xattr(ctx->kname->name)) + return do_set_acl(mnt_userns, dentry, ctx->kname->name, + ctx->kvalue, ctx->size); + return vfs_setxattr(mnt_userns, dentry, ctx->kname->name, ctx->kvalue, ctx->size, ctx->flags); } @@ -708,10 +713,11 @@ do_getxattr(struct user_namespace *mnt_userns, struct dentry *d, return -ENOMEM; } - error = vfs_getxattr(mnt_userns, d, kname, ctx->kvalue, ctx->size); + if (is_posix_acl_xattr(ctx->kname->name)) + error = do_get_acl(mnt_userns, d, kname, ctx->kvalue, ctx->size); + else + error = vfs_getxattr(mnt_userns, d, kname, ctx->kvalue, ctx->size); if (error > 0) { - if (is_posix_acl_xattr(kname)) - posix_acl_fix_xattr_to_user(ctx->kvalue, error); if (ctx->size && copy_to_user(ctx->value, ctx->kvalue, error)) error = -EFAULT; } else if (error == -ERANGE && ctx->size >= XATTR_SIZE_MAX) { @@ -886,6 +892,9 @@ removexattr(struct user_namespace *mnt_userns, struct dentry *d, if (error < 0) return error; + if (is_posix_acl_xattr(kname)) + return vfs_remove_acl(mnt_userns, d, kname); + return vfs_removexattr(mnt_userns, d, kname); } diff --git a/include/linux/posix_acl_xattr.h b/include/linux/posix_acl_xattr.h index bf30296389d7..c5d5fbc348dc 100644 --- a/include/linux/posix_acl_xattr.h +++ b/include/linux/posix_acl_xattr.h @@ -33,6 +33,8 @@ posix_acl_xattr_count(size_t size) } #ifdef CONFIG_FS_POSIX_ACL +struct posix_acl *posix_acl_from_xattr(struct user_namespace *user_ns, + const void *value, size_t size); void posix_acl_fix_xattr_from_user(void *value, size_t size); void posix_acl_fix_xattr_to_user(void *value, size_t size); void posix_acl_getxattr_idmapped_mnt(struct user_namespace *mnt_userns, @@ -42,6 +44,12 @@ ssize_t vfs_posix_acl_to_xattr(struct user_namespace *mnt_userns, struct inode *inode, const struct posix_acl *acl, void *buffer, size_t size); #else +static inline struct posix_acl * +posix_acl_from_xattr(struct user_namespace *user_ns, const void *value, + size_t size) +{ + return ERR_PTR(-EOPNOTSUPP); +} static inline void posix_acl_fix_xattr_from_user(void *value, size_t size) { } @@ -63,8 +71,6 @@ static inline ssize_t vfs_posix_acl_to_xattr(struct user_namespace *mnt_userns, } #endif -struct posix_acl *posix_acl_from_xattr(struct user_namespace *user_ns, - const void *value, size_t size); int posix_acl_to_xattr(struct user_namespace *user_ns, const struct posix_acl *acl, void *buffer, size_t size); struct posix_acl *vfs_set_acl_prepare(struct user_namespace *mnt_userns, -- cgit v1.2.3