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Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Pasha Tatashin , Pratyush Yadav , Randy Dunlap , Samiullah Khawaja , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , David Matlack Content-Type: text/plain; charset="UTF-8" From: Pasha Tatashin Allow userspace to pass a file-handler-specific argument structure when preserving or retrieving an FD via LUO. File handlers may need additional context during preservation or retrieval, such as a target FD, device location, or handler-specific parameters, without introducing separate ioctls for each file type. Whether the argument is required, optional, or unused is defined by the file handler. Extend struct liveupdate_session_preserve_fd and struct liveupdate_session_retrieve_fd with a 64-bit arg field pointing to a handler-defined argument structure that begins with a 32-bit size field. Because IOCTL_OP validates a minimum size up to the token field, existing callers passing the 16-byte struct remain compatible and have arg zero-filled by copy_struct_from_user(). Add parg and rarg (struct liveupdate_arg_spec) to struct liveupdate_file_ops, initialized via LIVEUPDATE_ARG(_struct, _min_last), which records the full struct size and minimum required size while enforcing at compile time that handler argument structures begin with a 32-bit size field. When arg is non-zero, LUO validates the minimum size and copies the user argument via copy_struct_from_user() up to the handler's expected size and passes the kernel copy in struct liveupdate_file_op_args, or returns -EOPNOTSUPP if the handler does not accept an argument. The argument only applies to the retrieve that restores the file. Retrieving a token that was already retrieved returns the existing file, so fail with -EBUSY if a non-zero argument is passed then, instead of silently ignoring it. Signed-off-by: Pasha Tatashin Signed-off-by: David Matlack --- include/linux/liveupdate.h | 44 +++++++++++++++++++ include/uapi/linux/liveupdate.h | 10 +++++ kernel/liveupdate/luo_file.c | 73 +++++++++++++++++++++++++++++--- kernel/liveupdate/luo_internal.h | 5 ++- kernel/liveupdate/luo_session.c | 6 ++- 5 files changed, 128 insertions(+), 10 deletions(-) diff --git a/include/linux/liveupdate.h b/include/linux/liveupdate.h index 6051abc0612c..7543f5d648d3 100644 --- a/include/linux/liveupdate.h +++ b/include/linux/liveupdate.h @@ -22,6 +22,36 @@ struct liveupdate_flb; struct liveupdate_session; struct file; +/** + * struct liveupdate_arg_spec - Specification of a file handler user argument. + * @size: Full size of the argument structure in the current kernel. + * @min_size: Minimum valid user-supplied size (offsetofend of the last + * required field). + */ +struct liveupdate_arg_spec { + size_t size; + size_t min_size; +}; + +/** + * LIVEUPDATE_ARG - Validated specification of a file handler argument struct. + * @_struct: The argument structure type. + * @_min_last: The last required member in @_struct. + * + * All file handler argument structures passed via + * &liveupdate_session_preserve_fd.arg or &liveupdate_session_retrieve_fd.arg + * must begin with a 32-bit @size field so they can be extended compatibly. + * Use this macro to initialize &liveupdate_file_ops.parg and + * &liveupdate_file_ops.rarg. + */ +#define LIVEUPDATE_ARG(_struct, _min_last) \ + { \ + .size = sizeof(_struct) + \ + BUILD_BUG_ON_ZERO(offsetof(_struct, size) != 0) + \ + BUILD_BUG_ON_ZERO(sizeof_field(_struct, size) != sizeof(u32)), \ + .min_size = offsetofend(_struct, _min_last), \ + } + /** * struct liveupdate_file_op_args - Arguments for file operation callbacks. * @handler: The file handler being called. @@ -40,6 +70,11 @@ struct file; * is not preserved. Set by the handler's .preserve() * callback, and must be freed in the handler's * .unpreserve() callback. + * @arg: Kernel copy of the user-provided argument for .preserve() + * and .retrieve(), or %NULL if none was provided. Allocated + * to the handler's expected argument size with any trailing + * bytes beyond the user-supplied size zero-filled. Valid + * only for the duration of the callback. * * This structure bundles all parameters for the file operation callbacks. * The 'data' and 'file' fields are used for both input and output. @@ -51,6 +86,7 @@ struct liveupdate_file_op_args { struct file *file; u64 serialized_data; void *private_data; + const void *arg; }; /** @@ -68,6 +104,12 @@ struct liveupdate_file_op_args { * resources in the session. * @finish: Required. Final cleanup in the new kernel. * @get_id: Optional. Returns a unique identifier for the file. + * @parg: Optional. Specification of the user argument structure + * accepted by @preserve, initialized via LIVEUPDATE_ARG(). If + * unset, non-zero user arguments are rejected with -EOPNOTSUPP. + * @rarg: Optional. Specification of the user argument structure + * accepted by @retrieve, initialized via LIVEUPDATE_ARG(). If + * unset, non-zero user arguments are rejected with -EOPNOTSUPP. * @owner: Module reference * * All operations (except can_preserve) receive a pointer to a @@ -84,6 +126,8 @@ struct liveupdate_file_ops { bool (*can_finish)(struct liveupdate_file_op_args *args); void (*finish)(struct liveupdate_file_op_args *args); unsigned long (*get_id)(struct file *file); + struct liveupdate_arg_spec parg; + struct liveupdate_arg_spec rarg; struct module *owner; }; diff --git a/include/uapi/linux/liveupdate.h b/include/uapi/linux/liveupdate.h index 4043d4038712..e806752c2fc6 100644 --- a/include/uapi/linux/liveupdate.h +++ b/include/uapi/linux/liveupdate.h @@ -126,6 +126,8 @@ struct liveupdate_ioctl_retrieve_session { * @size: Input; sizeof(struct liveupdate_session_preserve_fd) * @fd: Input; The user-space file descriptor to be preserved. * @token: Input; An opaque, unique token for preserved resource. + * @arg: Input; User-space pointer to a file-handler-specific argument + * structure starting with a 32-bit size field, or 0 if unused. * * Holds parameters for preserving a file descriptor. * @@ -149,6 +151,7 @@ struct liveupdate_session_preserve_fd { __u32 size; __s32 fd; __aligned_u64 token; + __aligned_u64 arg; }; #define LIVEUPDATE_SESSION_PRESERVE_FD \ @@ -160,6 +163,8 @@ struct liveupdate_session_preserve_fd { * @fd: Output; The new file descriptor representing the fully restored * kernel resource. * @token: Input; An opaque, token that was used to preserve the resource. + * @arg: Input; User-space pointer to a file-handler-specific argument + * structure starting with a 32-bit size field, or 0 if unused. * * Retrieve a previously preserved file descriptor. * @@ -173,12 +178,17 @@ struct liveupdate_session_preserve_fd { * attempts to retrieve the token fail with the same error code. Failed * retrieves are not retried. * + * Retrieving a token that was already retrieved successfully returns a new file + * descriptor for the same file. The @arg only applies to the retrieve that + * restores the file, so passing a non-zero @arg then fails with -EBUSY. + * * Return: 0 on success, negative error code on failure (e.g., invalid token). */ struct liveupdate_session_retrieve_fd { __u32 size; __s32 fd; __aligned_u64 token; + __aligned_u64 arg; }; #define LIVEUPDATE_SESSION_RETRIEVE_FD \ diff --git a/kernel/liveupdate/luo_file.c b/kernel/liveupdate/luo_file.c index a39992da504f..eeeb3b5ff2fa 100644 --- a/kernel/liveupdate/luo_file.c +++ b/kernel/liveupdate/luo_file.c @@ -126,6 +126,7 @@ #include #include #include +#include #include "luo_internal.h" static LIST_HEAD(luo_file_handler_list); @@ -202,11 +203,45 @@ static bool luo_token_is_used(struct luo_file_set *file_set, u64 token) return false; } +static int luo_copy_user_arg(u64 user_arg, const void **argp, + const struct liveupdate_arg_spec *spec) +{ + void *karg __free(kfree) = NULL; + void __user *uptr; + u32 user_size; + int err; + + if (!user_arg) + return 0; + if (!spec->size) + return -EOPNOTSUPP; + + uptr = u64_to_user_ptr(user_arg); + if (get_user(user_size, (u32 __user *)uptr)) + return -EFAULT; + if (user_size < spec->min_size) + return -EINVAL; + if (user_size > PAGE_SIZE) + return -E2BIG; + + karg = kmalloc(spec->size, GFP_KERNEL); + if (!karg) + return -ENOMEM; + + err = copy_struct_from_user(karg, spec->size, uptr, user_size); + if (err) + return err; + + *argp = no_free_ptr(karg); + return 0; +} + /** * luo_preserve_file - Initiate the preservation of a file descriptor. * @file_set: The file_set to which the preserved file will be added. * @token: A unique, user-provided identifier for the file. * @fd: The file descriptor to be preserved. + * @arg: User-space pointer to the handler argument structure, or 0. * * This function orchestrates the first phase of preserving a file. Upon entry, * it takes a reference to the 'struct file' via fget(), effectively making LUO @@ -222,9 +257,11 @@ static bool luo_token_is_used(struct luo_file_set *file_set, u64 token) * (allocates if needed). * 3. Iterates through registered handlers, calling can_preserve() to find one * compatible with the given @fd. - * 4. Calls the handler's .preserve() operation, which saves the file's state + * 4. Copies the user argument structure (if @arg is non-zero) according to the + * handler's parg specification. + * 5. Calls the handler's .preserve() operation, which saves the file's state * and returns an opaque private data handle. - * 5. Adds the new instance to the file_set's internal list. + * 6. Adds the new instance to the file_set's internal list. * * On success, LUO takes a reference to the 'struct file' and considers it * under its management until it is unpreserved or finished. @@ -239,10 +276,12 @@ static bool luo_token_is_used(struct luo_file_set *file_set, u64 token) * -EBADF if the file descriptor is invalid. * -ENOSPC if the file_set is full. * -ENOENT if no compatible handler is found. + * -EOPNOTSUPP if @arg is non-zero and the handler does not accept an arg. * -ENOMEM on memory allocation failure. * Other erros might be returned by .preserve(). */ -int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd) +int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd, + u64 arg) { struct liveupdate_file_op_args args = {0}; struct liveupdate_file_handler *fh; @@ -278,10 +317,14 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd) if (err) goto err_fput; + err = luo_copy_user_arg(arg, &args.arg, &fh->ops->parg); + if (err) + goto err_module_put; + err = xa_insert(&luo_preserved_files, luo_get_id(fh, file), file, GFP_KERNEL); if (err) - goto err_module_put; + goto err_free_arg; err = luo_flb_file_preserve(fh); if (err) @@ -305,6 +348,7 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd) if (err) goto err_kfree; + kfree(args.arg); luo_file->serialized_data = args.serialized_data; luo_file->private_data = args.private_data; list_add_tail(&luo_file->list, &file_set->files_list); @@ -318,6 +362,8 @@ int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd) luo_flb_file_unpreserve(fh); err_erase_xa: xa_erase(&luo_preserved_files, luo_get_id(fh, file)); +err_free_arg: + kfree(args.arg); err_module_put: module_put(fh->ops->owner); err_fput: @@ -547,6 +593,7 @@ void luo_file_unfreeze(struct luo_file_set *file_set, * luo_retrieve_file - Restores a preserved file from a file_set by its token. * @file_set: The file_set from which to retrieve the file. * @token: The unique token identifying the file to be restored. + * @arg: User-space pointer to the handler argument structure, or 0. * @filep: Output parameter; on success, this is populated with a pointer * to the newly retrieved 'struct file'. * @@ -566,9 +613,11 @@ void luo_file_unfreeze(struct luo_file_set *file_set, * kernel. * Return: 0 on success. Returns a negative errno on failure: * -ENOENT if no file with the matching token is found. + * -EOPNOTSUPP if @arg is non-zero and the handler does not accept an arg. + * -EBUSY if @arg is non-zero and the file was already retrieved. * Any error code returned by the handler's .retrieve() op. */ -int luo_retrieve_file(struct luo_file_set *file_set, u64 token, +int luo_retrieve_file(struct luo_file_set *file_set, u64 token, u64 arg, struct file **filep) { struct liveupdate_file_op_args args = {0}; @@ -596,6 +645,13 @@ int luo_retrieve_file(struct luo_file_set *file_set, u64 token, } if (luo_file->retrieve_status > 0) { + /* + * The argument only applies to the retrieve that restores the + * file. Don't silently ignore it. + */ + if (arg) + return -EBUSY; + /* * Someone is asking for this file again, so get a reference * for them. @@ -605,10 +661,15 @@ int luo_retrieve_file(struct luo_file_set *file_set, u64 token, return 0; } + err = luo_copy_user_arg(arg, &args.arg, &luo_file->fh->ops->rarg); + if (err) + return err; + args.handler = luo_file->fh; args.session = luo_session_from_file_set(file_set); args.serialized_data = luo_file->serialized_data; err = luo_file->fh->ops->retrieve(&args); + kfree(args.arg); if (err) { /* Keep the error code for later use. */ luo_file->retrieve_status = err; @@ -1007,6 +1068,6 @@ int liveupdate_get_file_incoming(struct liveupdate_session *s, u64 token, struct file **filep) { return luo_retrieve_file(luo_file_set_from_session_locked(s), - token, filep); + token, 0, filep); } EXPORT_SYMBOL_GPL(liveupdate_get_file_incoming); diff --git a/kernel/liveupdate/luo_internal.h b/kernel/liveupdate/luo_internal.h index dac6644bfb18..4126b71e9a2e 100644 --- a/kernel/liveupdate/luo_internal.h +++ b/kernel/liveupdate/luo_internal.h @@ -101,13 +101,14 @@ int __init luo_session_setup_incoming(u64 sessions_pa); int luo_session_serialize(void); int luo_session_deserialize(void); -int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd); +int luo_preserve_file(struct luo_file_set *file_set, u64 token, int fd, + u64 arg); void luo_file_unpreserve_files(struct luo_file_set *file_set); int luo_file_freeze(struct luo_file_set *file_set, struct luo_file_set_ser *file_set_ser); void luo_file_unfreeze(struct luo_file_set *file_set, struct luo_file_set_ser *file_set_ser); -int luo_retrieve_file(struct luo_file_set *file_set, u64 token, +int luo_retrieve_file(struct luo_file_set *file_set, u64 token, u64 arg, struct file **filep); int luo_file_finish(struct luo_file_set *file_set); int luo_file_deserialize(struct luo_file_set *file_set, diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c index f48e9a4185f9..ed9d53c7db77 100644 --- a/kernel/liveupdate/luo_session.c +++ b/kernel/liveupdate/luo_session.c @@ -267,7 +267,8 @@ static int luo_session_preserve_fd(struct luo_session *session, int err; guard(mutex)(&session->mutex); - err = luo_preserve_file(&session->file_set, argp->token, argp->fd); + err = luo_preserve_file(&session->file_set, argp->token, argp->fd, + argp->arg); if (err) return err; @@ -290,7 +291,8 @@ static int luo_session_retrieve_fd(struct luo_session *session, return argp->fd; mutex_lock(&session->mutex); - err = luo_retrieve_file(&session->file_set, argp->token, &file); + err = luo_retrieve_file(&session->file_set, argp->token, argp->arg, + &file); mutex_unlock(&session->mutex); if (err < 0) goto err_put_fd; -- 2.56.0.257.gf7497c7d27-goog