diff --git a/fs/fhandle.c b/fs/fhandle.c index e17029b1dc44..3e092ae6d142 100644 --- a/fs/fhandle.c +++ b/fs/fhandle.c @@ -187,17 +187,6 @@ static int get_path_from_fd(int fd, struct path *root) return 0; } -enum handle_to_path_flags { - HANDLE_CHECK_PERMS = (1 << 0), - HANDLE_CHECK_SUBTREE = (1 << 1), -}; - -struct handle_to_path_ctx { - struct path root; - enum handle_to_path_flags flags; - unsigned int fh_flags; -}; - static int vfs_dentry_acceptable(void *context, struct dentry *dentry) { struct handle_to_path_ctx *ctx = context; @@ -279,13 +268,13 @@ static int do_handle_to_path(struct file_handle *handle, struct path *path, return 0; } -static inline bool may_decode_fh(struct handle_to_path_ctx *ctx, - unsigned int o_flags) +static inline int may_decode_fh(struct handle_to_path_ctx *ctx, + unsigned int o_flags) { struct path *root = &ctx->root; if (capable(CAP_DAC_READ_SEARCH)) - return true; + return 0; /* * Allow relaxed permissions of file handles if the caller has @@ -309,7 +298,7 @@ static inline bool may_decode_fh(struct handle_to_path_ctx *ctx, * There's only one dentry for each directory inode (VFS rule)... */ if (!(o_flags & O_DIRECTORY)) - return false; + return -EPERM; if (ns_capable(root->mnt->mnt_sb->s_user_ns, CAP_SYS_ADMIN)) ctx->flags = HANDLE_CHECK_PERMS; @@ -319,14 +308,14 @@ static inline bool may_decode_fh(struct handle_to_path_ctx *ctx, !has_locked_children(real_mount(root->mnt), root->dentry)) ctx->flags = HANDLE_CHECK_PERMS | HANDLE_CHECK_SUBTREE; else - return false; + return -EPERM; /* Are we able to override DAC permissions? */ if (!ns_capable(current_user_ns(), CAP_DAC_READ_SEARCH)) - return false; + return -EPERM; ctx->fh_flags = EXPORT_FH_DIR_ONLY; - return true; + return 0; } static int handle_to_path(int mountdirfd, struct file_handle __user *ufh, @@ -336,15 +325,19 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh, struct file_handle f_handle; struct file_handle *handle = NULL; struct handle_to_path_ctx ctx = {}; + const struct export_operations *eops; retval = get_path_from_fd(mountdirfd, &ctx.root); if (retval) goto out_err; - if (!may_decode_fh(&ctx, o_flags)) { - retval = -EPERM; + eops = ctx.root.mnt->mnt_sb->s_export_op; + if (eops && eops->permission) + retval = eops->permission(&ctx, o_flags); + else + retval = may_decode_fh(&ctx, o_flags); + if (retval) goto out_path; - } if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) { retval = -EFAULT; diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h index c69b79b64466..a087606ace19 100644 --- a/include/linux/exportfs.h +++ b/include/linux/exportfs.h @@ -3,6 +3,7 @@ #define LINUX_EXPORTFS_H 1 #include +#include struct dentry; struct iattr; @@ -10,7 +11,6 @@ struct inode; struct iomap; struct super_block; struct vfsmount; -struct path; /* limit the handle size to NFSv4 handle size now */ #define MAX_HANDLE_SZ 128 @@ -157,6 +157,17 @@ struct fid { }; }; +enum handle_to_path_flags { + HANDLE_CHECK_PERMS = (1 << 0), + HANDLE_CHECK_SUBTREE = (1 << 1), +}; + +struct handle_to_path_ctx { + struct path root; + enum handle_to_path_flags flags; + unsigned int fh_flags; +}; + #define EXPORT_FH_CONNECTABLE 0x1 /* Encode file handle with parent */ #define EXPORT_FH_FID 0x2 /* File handle may be non-decodeable */ #define EXPORT_FH_DIR_ONLY 0x4 /* Only decode file handle for a directory */ @@ -226,6 +237,9 @@ struct fid { * is also a directory. In the event that it cannot be found, or storage * space cannot be allocated, a %ERR_PTR should be returned. * + * permission: + * Allow filesystems to specify a custom permission function. + * * open: * Allow filesystems to specify a custom open function. * @@ -255,6 +269,7 @@ struct export_operations { bool write, u32 *device_generation); int (*commit_blocks)(struct inode *inode, struct iomap *iomaps, int nr_iomaps, struct iattr *iattr); + int (*permission)(struct handle_to_path_ctx *ctx, unsigned int oflags); struct file * (*open)(struct path *path, unsigned int oflags); #define EXPORT_OP_NOWCC (0x1) /* don't collect v3 wcc data */ #define EXPORT_OP_NOSUBTREECHK (0x2) /* no subtree checking */