From 3abb1d90f5d930c6183534a624aa0158a71bc5eb Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 10 Aug 2016 11:23:44 -0400 Subject: kernfs: make kernfs_path*() behave in the style of strlcpy() kernfs_path*() functions always return the length of the full path but the path content is undefined if the length is larger than the provided buffer. This makes its behavior different from strlcpy() and requires error handling in all its users even when they don't care about truncation. In addition, the implementation can actully be simplified by making it behave properly in strlcpy() style. * Update kernfs_path_from_node_locked() to always fill up the buffer with path. If the buffer is not large enough, the output is truncated and terminated. * kernfs_path() no longer needs error handling. Make it a simple inline wrapper around kernfs_path_from_node(). * sysfs_warn_dup()'s use of kernfs_path() doesn't need error handling. Updated accordingly. * cgroup_path()'s use of kernfs_path() updated to retain the old behavior. Signed-off-by: Tejun Heo Acked-by: Greg Kroah-Hartman Acked-by: Serge Hallyn --- fs/kernfs/dir.c | 61 ++++++++++++++++----------------------------------------- fs/sysfs/dir.c | 6 +++--- 2 files changed, 20 insertions(+), 47 deletions(-) (limited to 'fs') diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index e57174d43683..09242aaa8829 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -110,8 +110,9 @@ static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a, * kn_to: /n1/n2/n3 [depth=3] * result: /../.. * - * return value: length of the string. If greater than buflen, - * then contents of buf are undefined. On error, -1 is returned. + * Returns the length of the full path. If the full length is equal to or + * greater than @buflen, @buf contains the truncated path with the trailing + * '\0'. On error, -errno is returned. */ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to, struct kernfs_node *kn_from, @@ -119,9 +120,8 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to, { struct kernfs_node *kn, *common; const char parent_str[] = "/.."; - size_t depth_from, depth_to, len = 0, nlen = 0; - char *p; - int i; + size_t depth_from, depth_to, len = 0; + int i, j; if (!kn_from) kn_from = kernfs_root(kn_to)->kn; @@ -131,7 +131,7 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to, common = kernfs_common_ancestor(kn_from, kn_to); if (WARN_ON(!common)) - return -1; + return -EINVAL; depth_to = kernfs_depth(common, kn_to); depth_from = kernfs_depth(common, kn_from); @@ -144,22 +144,16 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to, len < buflen ? buflen - len : 0); /* Calculate how many bytes we need for the rest */ - for (kn = kn_to; kn != common; kn = kn->parent) - nlen += strlen(kn->name) + 1; - - if (len + nlen >= buflen) - return len + nlen; - - p = buf + len + nlen; - *p = '\0'; - for (kn = kn_to; kn != common; kn = kn->parent) { - size_t tmp = strlen(kn->name); - p -= tmp; - memcpy(p, kn->name, tmp); - *(--p) = '/'; + for (i = depth_to - 1; i >= 0; i--) { + for (kn = kn_to, j = 0; j < i; j++) + kn = kn->parent; + len += strlcpy(buf + len, "/", + len < buflen ? buflen - len : 0); + len += strlcpy(buf + len, kn->name, + len < buflen ? buflen - len : 0); } - return len + nlen; + return len; } /** @@ -220,8 +214,9 @@ size_t kernfs_path_len(struct kernfs_node *kn) * path (which includes '..'s) as needed to reach from @from to @to is * returned. * - * If @buf isn't long enough, the return value will be greater than @buflen - * and @buf contents are undefined. + * Returns the length of the full path. If the full length is equal to or + * greater than @buflen, @buf contains the truncated path with the trailing + * '\0'. On error, -errno is returned. */ int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from, char *buf, size_t buflen) @@ -236,28 +231,6 @@ int kernfs_path_from_node(struct kernfs_node *to, struct kernfs_node *from, } EXPORT_SYMBOL_GPL(kernfs_path_from_node); -/** - * kernfs_path - build full path of a given node - * @kn: kernfs_node of interest - * @buf: buffer to copy @kn's name into - * @buflen: size of @buf - * - * Builds and returns the full path of @kn in @buf of @buflen bytes. The - * path is built from the end of @buf so the returned pointer usually - * doesn't match @buf. If @buf isn't long enough, @buf is nul terminated - * and %NULL is returned. - */ -char *kernfs_path(struct kernfs_node *kn, char *buf, size_t buflen) -{ - int ret; - - ret = kernfs_path_from_node(kn, NULL, buf, buflen); - if (ret < 0 || ret >= buflen) - return NULL; - return buf; -} -EXPORT_SYMBOL_GPL(kernfs_path); - /** * pr_cont_kernfs_name - pr_cont name of a kernfs_node * @kn: kernfs_node of interest diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index 94374e435025..2b67bda2021b 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -21,14 +21,14 @@ DEFINE_SPINLOCK(sysfs_symlink_target_lock); void sysfs_warn_dup(struct kernfs_node *parent, const char *name) { - char *buf, *path = NULL; + char *buf; buf = kzalloc(PATH_MAX, GFP_KERNEL); if (buf) - path = kernfs_path(parent, buf, PATH_MAX); + kernfs_path(parent, buf, PATH_MAX); WARN(1, KERN_WARNING "sysfs: cannot create duplicate filename '%s/%s'\n", - path, name); + buf, name); kfree(buf); } -- cgit v1.2.3 From bb09c8634b1e484b8840fb2384d55739bfcb68bd Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 10 Aug 2016 11:23:44 -0400 Subject: kernfs: remove kernfs_path_len() It doesn't have any in-kernel user and the same result can be obtained from kernfs_path(@kn, NULL, 0). Remove it. Signed-off-by: Tejun Heo Acked-by: Greg Kroah-Hartman Cc: Serge Hallyn --- fs/kernfs/dir.c | 23 ----------------------- include/linux/kernfs.h | 4 ---- 2 files changed, 27 deletions(-) (limited to 'fs') diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 09242aaa8829..6e7fd37615f8 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -179,29 +179,6 @@ int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen) return ret; } -/** - * kernfs_path_len - determine the length of the full path of a given node - * @kn: kernfs_node of interest - * - * The returned length doesn't include the space for the terminating '\0'. - */ -size_t kernfs_path_len(struct kernfs_node *kn) -{ - size_t len = 0; - unsigned long flags; - - spin_lock_irqsave(&kernfs_rename_lock, flags); - - do { - len += strlen(kn->name) + 1; - kn = kn->parent; - } while (kn && kn->parent); - - spin_unlock_irqrestore(&kernfs_rename_lock, flags); - - return len; -} - /** * kernfs_path_from_node - build path of node @to relative to @from. * @from: parent kernfs_node relative to which we need to build the path diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 4a02b1b49821..7056238fd9f5 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -269,7 +269,6 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn) } int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen); -size_t kernfs_path_len(struct kernfs_node *kn); int kernfs_path_from_node(struct kernfs_node *root_kn, struct kernfs_node *kn, char *buf, size_t buflen); void pr_cont_kernfs_name(struct kernfs_node *kn); @@ -340,9 +339,6 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn) static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen) { return -ENOSYS; } -static inline size_t kernfs_path_len(struct kernfs_node *kn) -{ return 0; } - static inline int kernfs_path_from_node(struct kernfs_node *root_kn, struct kernfs_node *kn, char *buf, size_t buflen) -- cgit v1.2.3