From f454fa610a69b93e7ed4de739e736f988d95c2d2 Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Thu, 16 Jul 2020 11:42:17 +0300 Subject: [PATCH] fanotify: use struct fanotify_info to parcel the variable size buffer An fanotify event name is always recorded relative to a dir fh. Encapsulate the name_len member of fanotify_name_event in a new struct fanotify_info, which describes the parceling of the variable size buffer of an fanotify_name_event. The dir_fh member of fanotify_name_event is renamed to _dir_fh and is not accessed directly, but via the fanotify_info_dir_fh() accessor. Although the dir_fh len information is already available in struct fanotify_fh, we store it also in dif_fh_totlen member of fanotify_info, including the size of fanotify_fh header, so we know the offset of the name in the buffer without looking inside the dir_fh. We also add a file_fh_totlen member to allow packing another file handle in the variable size buffer after the dir_fh and before the name. We are going to use that space to store the child fid. Link: https://lore.kernel.org/r/20200716084230.30611-10-amir73il@gmail.com Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara --- fs/notify/fanotify/fanotify.c | 66 ++++++++++++++++++++------- fs/notify/fanotify/fanotify.h | 91 ++++++++++++++++++++++++++++++++------ fs/notify/fanotify/fanotify_user.c | 25 +++++------ 3 files changed, 139 insertions(+), 43 deletions(-) diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index b8c04a6..31fd41e 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -49,22 +49,44 @@ static bool fanotify_fid_event_equal(struct fanotify_fid_event *ffe1, fanotify_fh_equal(&ffe1->object_fh, &ffe2->object_fh); } +static bool fanotify_info_equal(struct fanotify_info *info1, + struct fanotify_info *info2) +{ + if (info1->dir_fh_totlen != info2->dir_fh_totlen || + info1->file_fh_totlen != info2->file_fh_totlen || + info1->name_len != info2->name_len) + return false; + + if (info1->dir_fh_totlen && + !fanotify_fh_equal(fanotify_info_dir_fh(info1), + fanotify_info_dir_fh(info2))) + return false; + + if (info1->file_fh_totlen && + !fanotify_fh_equal(fanotify_info_file_fh(info1), + fanotify_info_file_fh(info2))) + return false; + + return !info1->name_len || + !memcmp(fanotify_info_name(info1), fanotify_info_name(info2), + info1->name_len); +} + static bool fanotify_name_event_equal(struct fanotify_name_event *fne1, struct fanotify_name_event *fne2) { - /* Do not merge name events without dir fh */ - if (!fne1->dir_fh.len) - return false; + struct fanotify_info *info1 = &fne1->info; + struct fanotify_info *info2 = &fne2->info; - if (fne1->name_len != fne2->name_len || - !fanotify_fh_equal(&fne1->dir_fh, &fne2->dir_fh)) + /* Do not merge name events without dir fh */ + if (!info1->dir_fh_totlen) return false; - return !memcmp(fne1->name, fne2->name, fne1->name_len); + return fanotify_info_equal(info1, info2); } static bool fanotify_should_merge(struct fsnotify_event *old_fsn, - struct fsnotify_event *new_fsn) + struct fsnotify_event *new_fsn) { struct fanotify_event *old, *new; @@ -276,8 +298,14 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group, return test_mask & user_mask; } -static void fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode, - gfp_t gfp) +/* + * Encode fanotify_fh. + * + * Return total size of encoded fh including fanotify_fh header. + * Return 0 on failure to encode. + */ +static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode, + gfp_t gfp) { int dwords, type, bytes = 0; char *ext_buf = NULL; @@ -287,7 +315,7 @@ static void fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode, fh->type = FILEID_ROOT; fh->len = 0; if (!inode) - return; + return 0; dwords = 0; err = -ENOENT; @@ -315,7 +343,7 @@ static void fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode, fh->type = type; fh->len = bytes; - return; + return FANOTIFY_FH_HDR_LEN + bytes; out_err: pr_warn_ratelimited("fanotify: failed to encode fid (type=%d, len=%d, err=%i)\n", @@ -325,6 +353,7 @@ out_err: /* Report the event without a file identifier on encode error */ fh->type = FILEID_INVALID; fh->len = 0; + return 0; } /* @@ -401,6 +430,8 @@ static struct fanotify_event *fanotify_alloc_name_event(struct inode *id, gfp_t gfp) { struct fanotify_name_event *fne; + struct fanotify_info *info; + struct fanotify_fh *dfh; fne = kmalloc(sizeof(*fne) + file_name->len + 1, gfp); if (!fne) @@ -408,9 +439,11 @@ static struct fanotify_event *fanotify_alloc_name_event(struct inode *id, fne->fae.type = FANOTIFY_EVENT_TYPE_FID_NAME; fne->fsid = *fsid; - fanotify_encode_fh(&fne->dir_fh, id, gfp); - fne->name_len = file_name->len; - strcpy(fne->name, file_name->name); + info = &fne->info; + fanotify_info_init(info); + dfh = fanotify_info_dir_fh(info); + info->dir_fh_totlen = fanotify_encode_fh(dfh, id, gfp); + fanotify_info_copy_name(info, file_name); return &fne->fae; } @@ -626,9 +659,10 @@ static void fanotify_free_fid_event(struct fanotify_event *event) static void fanotify_free_name_event(struct fanotify_event *event) { struct fanotify_name_event *fne = FANOTIFY_NE(event); + struct fanotify_fh *dfh = fanotify_info_dir_fh(&fne->info); - if (fanotify_fh_has_ext_buf(&fne->dir_fh)) - kfree(fanotify_fh_ext_buf(&fne->dir_fh)); + if (fanotify_fh_has_ext_buf(dfh)) + kfree(fanotify_fh_ext_buf(dfh)); kfree(fne); } diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h index 1b2a3bb..5e104fc 100644 --- a/fs/notify/fanotify/fanotify.h +++ b/fs/notify/fanotify/fanotify.h @@ -23,11 +23,29 @@ enum { * stored in either the first or last 2 dwords. */ #define FANOTIFY_INLINE_FH_LEN (3 << 2) +#define FANOTIFY_FH_HDR_LEN offsetof(struct fanotify_fh, buf) +/* Fixed size struct for file handle */ struct fanotify_fh { - unsigned char buf[FANOTIFY_INLINE_FH_LEN]; u8 type; u8 len; + u8 pad[2]; + unsigned char buf[FANOTIFY_INLINE_FH_LEN]; +} __aligned(4); + +/* Variable size struct for dir file handle + child file handle + name */ +struct fanotify_info { + /* size of dir_fh/file_fh including fanotify_fh hdr size */ + u8 dir_fh_totlen; + u8 file_fh_totlen; + u8 name_len; + u8 pad; + unsigned char buf[]; + /* + * (struct fanotify_fh) dir_fh starts at buf[0] + * (optional) file_fh starts at buf[dir_fh_totlen] + * name starts at buf[dir_fh_totlen + file_fh_totlen] + */ } __aligned(4); static inline bool fanotify_fh_has_ext_buf(struct fanotify_fh *fh) @@ -37,6 +55,7 @@ static inline bool fanotify_fh_has_ext_buf(struct fanotify_fh *fh) static inline char **fanotify_fh_ext_buf_ptr(struct fanotify_fh *fh) { + BUILD_BUG_ON(FANOTIFY_FH_HDR_LEN % 4); BUILD_BUG_ON(__alignof__(char *) - 4 + sizeof(char *) > FANOTIFY_INLINE_FH_LEN); return (char **)ALIGN((unsigned long)(fh->buf), __alignof__(char *)); @@ -52,6 +71,56 @@ static inline void *fanotify_fh_buf(struct fanotify_fh *fh) return fanotify_fh_has_ext_buf(fh) ? fanotify_fh_ext_buf(fh) : fh->buf; } +static inline int fanotify_info_dir_fh_len(struct fanotify_info *info) +{ + if (!info->dir_fh_totlen || + WARN_ON_ONCE(info->dir_fh_totlen < FANOTIFY_FH_HDR_LEN)) + return 0; + + return info->dir_fh_totlen - FANOTIFY_FH_HDR_LEN; +} + +static inline struct fanotify_fh *fanotify_info_dir_fh(struct fanotify_info *info) +{ + BUILD_BUG_ON(offsetof(struct fanotify_info, buf) % 4); + + return (struct fanotify_fh *)info->buf; +} + +static inline int fanotify_info_file_fh_len(struct fanotify_info *info) +{ + if (!info->file_fh_totlen || + WARN_ON_ONCE(info->file_fh_totlen < FANOTIFY_FH_HDR_LEN)) + return 0; + + return info->file_fh_totlen - FANOTIFY_FH_HDR_LEN; +} + +static inline struct fanotify_fh *fanotify_info_file_fh(struct fanotify_info *info) +{ + return (struct fanotify_fh *)(info->buf + info->dir_fh_totlen); +} + +static inline const char *fanotify_info_name(struct fanotify_info *info) +{ + return info->buf + info->dir_fh_totlen + info->file_fh_totlen; +} + +static inline void fanotify_info_init(struct fanotify_info *info) +{ + info->dir_fh_totlen = 0; + info->file_fh_totlen = 0; + info->name_len = 0; +} + +static inline void fanotify_info_copy_name(struct fanotify_info *info, + const struct qstr *name) +{ + info->name_len = name->len; + strcpy(info->buf + info->dir_fh_totlen + info->file_fh_totlen, + name->name); +} + /* * Common structure for fanotify events. Concrete structs are allocated in * fanotify_handle_event() and freed when the information is retrieved by @@ -96,9 +165,9 @@ FANOTIFY_FE(struct fanotify_event *event) struct fanotify_name_event { struct fanotify_event fae; __kernel_fsid_t fsid; - struct fanotify_fh dir_fh; - u8 name_len; - char name[]; + struct fanotify_info info; + /* Reserve space in info.buf[] - access with fanotify_info_dir_fh() */ + struct fanotify_fh _dir_fh; }; static inline struct fanotify_name_event * @@ -126,11 +195,11 @@ static inline struct fanotify_fh *fanotify_event_object_fh( return NULL; } -static inline struct fanotify_fh *fanotify_event_dir_fh( +static inline struct fanotify_info *fanotify_event_info( struct fanotify_event *event) { if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME) - return &FANOTIFY_NE(event)->dir_fh; + return &FANOTIFY_NE(event)->info; else return NULL; } @@ -142,15 +211,11 @@ static inline int fanotify_event_object_fh_len(struct fanotify_event *event) return fh ? fh->len : 0; } -static inline bool fanotify_event_has_name(struct fanotify_event *event) +static inline int fanotify_event_dir_fh_len(struct fanotify_event *event) { - return event->type == FANOTIFY_EVENT_TYPE_FID_NAME; -} + struct fanotify_info *info = fanotify_event_info(event); -static inline int fanotify_event_name_len(struct fanotify_event *event) -{ - return fanotify_event_has_name(event) ? - FANOTIFY_NE(event)->name_len : 0; + return info ? fanotify_info_dir_fh_len(info) : 0; } struct fanotify_path_event { diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 16d70a8..3842ef0 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -66,19 +66,17 @@ static int fanotify_fid_info_len(int fh_len, int name_len) static int fanotify_event_info_len(struct fanotify_event *event) { - int info_len = 0; + struct fanotify_info *info = fanotify_event_info(event); + int dir_fh_len = fanotify_event_dir_fh_len(event); int fh_len = fanotify_event_object_fh_len(event); + int info_len = 0; + + if (dir_fh_len) + info_len += fanotify_fid_info_len(dir_fh_len, info->name_len); if (fh_len) info_len += fanotify_fid_info_len(fh_len, 0); - if (fanotify_event_name_len(event)) { - struct fanotify_name_event *fne = FANOTIFY_NE(event); - - info_len += fanotify_fid_info_len(fne->dir_fh.len, - fne->name_len); - } - return info_len; } @@ -305,6 +303,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, { struct fanotify_event_metadata metadata; struct path *path = fanotify_event_path(event); + struct fanotify_info *info = fanotify_event_info(event); struct file *f = NULL; int ret, fd = FAN_NOFD; @@ -346,13 +345,11 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, fd_install(fd, f); /* Event info records order is: dir fid + name, child fid */ - if (fanotify_event_name_len(event)) { - struct fanotify_name_event *fne = FANOTIFY_NE(event); - + if (fanotify_event_dir_fh_len(event)) { ret = copy_info_to_user(fanotify_event_fsid(event), - fanotify_event_dir_fh(event), - fne->name, fne->name_len, - buf, count); + fanotify_info_dir_fh(info), + fanotify_info_name(info), + info->name_len, buf, count); if (ret < 0) return ret; -- 2.7.4