diff options
| -rw-r--r-- | fs/Makefile | 2 | ||||
| -rw-r--r-- | fs/d_path.c | 470 | ||||
| -rw-r--r-- | fs/dcache.c | 467 |
3 files changed, 472 insertions, 467 deletions
diff --git a/fs/Makefile b/fs/Makefile index add789ea270a..c9375fd2c8c4 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -11,7 +11,7 @@ obj-y := open.o read_write.o file_table.o super.o \ ioctl.o readdir.o select.o dcache.o inode.o \ attr.o bad_inode.o file.o filesystems.o namespace.o \ seq_file.o xattr.o libfs.o fs-writeback.o \ - pnode.o splice.o sync.o utimes.o \ + pnode.o splice.o sync.o utimes.o d_path.o \ stack.o fs_struct.o statfs.o fs_pin.o nsfs.o ifeq ($(CONFIG_BLOCK),y) diff --git a/fs/d_path.c b/fs/d_path.c new file mode 100644 index 000000000000..e8fce6b1174f --- /dev/null +++ b/fs/d_path.c @@ -0,0 +1,470 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#include <linux/syscalls.h> +#include <linux/export.h> +#include <linux/uaccess.h> +#include <linux/fs_struct.h> +#include <linux/fs.h> +#include <linux/slab.h> +#include <linux/prefetch.h> +#include "mount.h" + +static int prepend(char **buffer, int *buflen, const char *str, int namelen) +{ + *buflen -= namelen; + if (*buflen < 0) + return -ENAMETOOLONG; + *buffer -= namelen; + memcpy(*buffer, str, namelen); + return 0; +} + +/** + * prepend_name - prepend a pathname in front of current buffer pointer + * @buffer: buffer pointer + * @buflen: allocated length of the buffer + * @name: name string and length qstr structure + * + * With RCU path tracing, it may race with d_move(). Use READ_ONCE() to + * make sure that either the old or the new name pointer and length are + * fetched. However, there may be mismatch between length and pointer. + * The length cannot be trusted, we need to copy it byte-by-byte until + * the length is reached or a null byte is found. It also prepends "/" at + * the beginning of the name. The sequence number check at the caller will + * retry it again when a d_move() does happen. So any garbage in the buffer + * due to mismatched pointer and length will be discarded. + * + * Load acquire is needed to make sure that we see that terminating NUL. + */ +static int prepend_name(char **buffer, int *buflen, const struct qstr *name) +{ + const char *dname = smp_load_acquire(&name->name); /* ^^^ */ + u32 dlen = READ_ONCE(name->len); + char *p; + + *buflen -= dlen + 1; + if (*buflen < 0) + return -ENAMETOOLONG; + p = *buffer -= dlen + 1; + *p++ = '/'; + while (dlen--) { + char c = *dname++; + if (!c) + break; + *p++ = c; + } + return 0; +} + +/** + * prepend_path - Prepend path string to a buffer + * @path: the dentry/vfsmount to report + * @root: root vfsmnt/dentry + * @buffer: pointer to the end of the buffer + * @buflen: pointer to buffer length + * + * The function will first try to write out the pathname without taking any + * lock other than the RCU read lock to make sure that dentries won't go away. + * It only checks the sequence number of the global rename_lock as any change + * in the dentry's d_seq will be preceded by changes in the rename_lock + * sequence number. If the sequence number had been changed, it will restart + * the whole pathname back-tracing sequence again by taking the rename_lock. + * In this case, there is no need to take the RCU read lock as the recursive + * parent pointer references will keep the dentry chain alive as long as no + * rename operation is performed. + */ +static int prepend_path(const struct path *path, + const struct path *root, + char **buffer, int *buflen) +{ + struct dentry *dentry; + struct vfsmount *vfsmnt; + struct mount *mnt; + int error = 0; + unsigned seq, m_seq = 0; + char *bptr; + int blen; + + rcu_read_lock(); +restart_mnt: + read_seqbegin_or_lock(&mount_lock, &m_seq); + seq = 0; + rcu_read_lock(); +restart: + bptr = *buffer; + blen = *buflen; + error = 0; + dentry = path->dentry; + vfsmnt = path->mnt; + mnt = real_mount(vfsmnt); + read_seqbegin_or_lock(&rename_lock, &seq); + while (dentry != root->dentry || vfsmnt != root->mnt) { + struct dentry * parent; + + if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { + struct mount *parent = READ_ONCE(mnt->mnt_parent); + /* Escaped? */ + if (dentry != vfsmnt->mnt_root) { + bptr = *buffer; + blen = *buflen; + error = 3; + break; + } + /* Global root? */ + if (mnt != parent) { + dentry = READ_ONCE(mnt->mnt_mountpoint); + mnt = parent; + vfsmnt = &mnt->mnt; + continue; + } + if (!error) + error = is_mounted(vfsmnt) ? 1 : 2; + break; + } + parent = dentry->d_parent; + prefetch(parent); + error = prepend_name(&bptr, &blen, &dentry->d_name); + if (error) + break; + + dentry = parent; + } + if (!(seq & 1)) + rcu_read_unlock(); + if (need_seqretry(&rename_lock, seq)) { + seq = 1; + goto restart; + } + done_seqretry(&rename_lock, seq); + + if (!(m_seq & 1)) + rcu_read_unlock(); + if (need_seqretry(&mount_lock, m_seq)) { + m_seq = 1; + goto restart_mnt; + } + done_seqretry(&mount_lock, m_seq); + + if (error >= 0 && bptr == *buffer) { + if (--blen < 0) + error = -ENAMETOOLONG; + else + *--bptr = '/'; + } + *buffer = bptr; + *buflen = blen; + return error; +} + +/** + * __d_path - return the path of a dentry + * @path: the dentry/vfsmount to report + * @root: root vfsmnt/dentry + * @buf: buffer to return value in + * @buflen: buffer length + * + * Convert a dentry into an ASCII path name. + * + * Returns a pointer into the buffer or an error code if the + * path was too long. + * + * "buflen" should be positive. + * + * If the path is not reachable from the supplied root, return %NULL. + */ +char *__d_path(const struct path *path, + const struct path *root, + char *buf, int buflen) +{ + char *res = buf + buflen; + int error; + + prepend(&res, &buflen, "\0", 1); + error = prepend_path(path, root, &res, &buflen); + + if (error < 0) + return ERR_PTR(error); + if (error > 0) + return NULL; + return res; +} + +char *d_absolute_path(const struct path *path, + char *buf, int buflen) +{ + struct path root = {}; + char *res = buf + buflen; + int error; + + prepend(&res, &buflen, "\0", 1); + error = prepend_path(path, &root, &res, &buflen); + + if (error > 1) + error = -EINVAL; + if (error < 0) + return ERR_PTR(error); + return res; +} + +/* + * same as __d_path but appends "(deleted)" for unlinked files. + */ +static int path_with_deleted(const struct path *path, + const struct path *root, + char **buf, int *buflen) +{ + prepend(buf, buflen, "\0", 1); + if (d_unlinked(path->dentry)) { + int error = prepend(buf, buflen, " (deleted)", 10); + if (error) + return error; + } + + return prepend_path(path, root, buf, buflen); +} + +static int prepend_unreachable(char **buffer, int *buflen) +{ + return prepend(buffer, buflen, "(unreachable)", 13); +} + +static void get_fs_root_rcu(struct fs_struct *fs, struct path *root) +{ + unsigned seq; + + do { + seq = read_seqcount_begin(&fs->seq); + *root = fs->root; + } while (read_seqcount_retry(&fs->seq, seq)); +} + +/** + * d_path - return the path of a dentry + * @path: path to report + * @buf: buffer to return value in + * @buflen: buffer length + * + * Convert a dentry into an ASCII path name. If the entry has been deleted + * the string " (deleted)" is appended. Note that this is ambiguous. + * + * Returns a pointer into the buffer or an error code if the path was + * too long. Note: Callers should use the returned pointer, not the passed + * in buffer, to use the name! The implementation often starts at an offset + * into the buffer, and may leave 0 bytes at the start. + * + * "buflen" should be positive. + */ +char *d_path(const struct path *path, char *buf, int buflen) +{ + char *res = buf + buflen; + struct path root; + int error; + + /* + * We have various synthetic filesystems that never get mounted. On + * these filesystems dentries are never used for lookup purposes, and + * thus don't need to be hashed. They also don't need a name until a + * user wants to identify the object in /proc/pid/fd/. The little hack + * below allows us to generate a name for these objects on demand: + * + * Some pseudo inodes are mountable. When they are mounted + * path->dentry == path->mnt->mnt_root. In that case don't call d_dname + * and instead have d_path return the mounted path. + */ + if (path->dentry->d_op && path->dentry->d_op->d_dname && + (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root)) + return path->dentry->d_op->d_dname(path->dentry, buf, buflen); + + rcu_read_lock(); + get_fs_root_rcu(current->fs, &root); + error = path_with_deleted(path, &root, &res, &buflen); + rcu_read_unlock(); + + if (error < 0) + res = ERR_PTR(error); + return res; +} +EXPORT_SYMBOL(d_path); + +/* + * Helper function for dentry_operations.d_dname() members + */ +char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen, + const char *fmt, ...) +{ + va_list args; + char temp[64]; + int sz; + + va_start(args, fmt); + sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1; + va_end(args); + + if (sz > sizeof(temp) || sz > buflen) + return ERR_PTR(-ENAMETOOLONG); + + buffer += buflen - sz; + return memcpy(buffer, temp, sz); +} + +char *simple_dname(struct dentry *dentry, char *buffer, int buflen) +{ + char *end = buffer + buflen; + /* these dentries are never renamed, so d_lock is not needed */ + if (prepend(&end, &buflen, " (deleted)", 11) || + prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) || + prepend(&end, &buflen, "/", 1)) + end = ERR_PTR(-ENAMETOOLONG); + return end; +} +EXPORT_SYMBOL(simple_dname); + +/* + * Write full pathname from the root of the filesystem into the buffer. + */ +static char *__dentry_path(struct dentry *d, char *buf, int buflen) +{ + struct dentry *dentry; + char *end, *retval; + int len, seq = 0; + int error = 0; + + if (buflen < 2) + goto Elong; + + rcu_read_lock(); +restart: + dentry = d; + end = buf + buflen; + len = buflen; + prepend(&end, &len, "\0", 1); + /* Get '/' right */ + retval = end-1; + *retval = '/'; + read_seqbegin_or_lock(&rename_lock, &seq); + while (!IS_ROOT(dentry)) { + struct dentry *parent = dentry->d_parent; + + prefetch(parent); + error = prepend_name(&end, &len, &dentry->d_name); + if (error) + break; + + retval = end; + dentry = parent; + } + if (!(seq & 1)) + rcu_read_unlock(); + if (need_seqretry(&rename_lock, seq)) { + seq = 1; + goto restart; + } + done_seqretry(&rename_lock, seq); + if (error) + goto Elong; + return retval; +Elong: + return ERR_PTR(-ENAMETOOLONG); +} + +char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen) +{ + return __dentry_path(dentry, buf, buflen); +} +EXPORT_SYMBOL(dentry_path_raw); + +char *dentry_path(struct dentry *dentry, char *buf, int buflen) +{ + char *p = NULL; + char *retval; + + if (d_unlinked(dentry)) { + p = buf + buflen; + if (prepend(&p, &buflen, "//deleted", 10) != 0) + goto Elong; + buflen++; + } + retval = __dentry_path(dentry, buf, buflen); + if (!IS_ERR(retval) && p) + *p = '/'; /* restore '/' overriden with '\0' */ + return retval; +Elong: + return ERR_PTR(-ENAMETOOLONG); +} + +static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root, + struct path *pwd) +{ + unsigned seq; + + do { + seq = read_seqcount_begin(&fs->seq); + *root = fs->root; + *pwd = fs->pwd; + } while (read_seqcount_retry(&fs->seq, seq)); +} + +/* + * NOTE! The user-level library version returns a + * character pointer. The kernel system call just + * returns the length of the buffer filled (which + * includes the ending '\0' character), or a negative + * error value. So libc would do something like + * + * char *getcwd(char * buf, size_t size) + * { + * int retval; + * + * retval = sys_getcwd(buf, size); + * if (retval >= 0) + * return buf; + * errno = -retval; + * return NULL; + * } + */ +SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) +{ + int error; + struct path pwd, root; + char *page = __getname(); + + if (!page) + return -ENOMEM; + + rcu_read_lock(); + get_fs_root_and_pwd_rcu(current->fs, &root, &pwd); + + error = -ENOENT; + if (!d_unlinked(pwd.dentry)) { + unsigned long len; + char *cwd = page + PATH_MAX; + int buflen = PATH_MAX; + + prepend(&cwd, &buflen, "\0", 1); + error = prepend_path(&pwd, &root, &cwd, &buflen); + rcu_read_unlock(); + + if (error < 0) + goto out; + + /* Unreachable from current root */ + if (error > 0) { + error = prepend_unreachable(&cwd, &buflen); + if (error) + goto out; + } + + error = -ERANGE; + len = PATH_MAX + page - cwd; + if (len <= size) { + error = len; + if (copy_to_user(buf, cwd, len)) + error = -EFAULT; + } + } else { + rcu_read_unlock(); + } + +out: + __putname(page); + return error; +} diff --git a/fs/dcache.c b/fs/dcache.c index 91626643fc86..c870343f904f 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -14,7 +14,7 @@ * the dcache entry is deleted or garbage collected. */ -#include <linux/syscalls.h> +#include <linux/ratelimit.h> #include <linux/string.h> #include <linux/mm.h> #include <linux/fs.h> @@ -24,15 +24,11 @@ #include <linux/hash.h> #include <linux/cache.h> #include <linux/export.h> -#include <linux/mount.h> -#include <linux/uaccess.h> #include <linux/security.h> #include <linux/seqlock.h> #include <linux/bootmem.h> -#include <linux/fs_struct.h> #include <linux/bit_spinlock.h> #include <linux/rculist_bl.h> -#include <linux/prefetch.h> #include <linux/list_lru.h> #include "internal.h" #include "mount.h" @@ -3072,467 +3068,6 @@ out: } EXPORT_SYMBOL(d_splice_alias); -static int prepend(char **buffer, int *buflen, const char *str, int namelen) -{ - *buflen -= namelen; - if (*buflen < 0) - return -ENAMETOOLONG; - *buffer -= namelen; - memcpy(*buffer, str, namelen); - return 0; -} - -/** - * prepend_name - prepend a pathname in front of current buffer pointer - * @buffer: buffer pointer - * @buflen: allocated length of the buffer - * @name: name string and length qstr structure - * - * With RCU path tracing, it may race with d_move(). Use READ_ONCE() to - * make sure that either the old or the new name pointer and length are - * fetched. However, there may be mismatch between length and pointer. - * The length cannot be trusted, we need to copy it byte-by-byte until - * the length is reached or a null byte is found. It also prepends "/" at - * the beginning of the name. The sequence number check at the caller will - * retry it again when a d_move() does happen. So any garbage in the buffer - * due to mismatched pointer and length will be discarded. - * - * Load acquire is needed to make sure that we see that terminating NUL. - */ -static int prepend_name(char **buffer, int *buflen, const struct qstr *name) -{ - const char *dname = smp_load_acquire(&name->name); /* ^^^ */ - u32 dlen = READ_ONCE(name->len); - char *p; - - *buflen -= dlen + 1; - if (*buflen < 0) - return -ENAMETOOLONG; - p = *buffer -= dlen + 1; - *p++ = '/'; - while (dlen--) { - char c = *dname++; - if (!c) - break; - *p++ = c; - } - return 0; -} - -/** - * prepend_path - Prepend path string to a buffer - * @path: the dentry/vfsmount to report - * @root: root vfsmnt/dentry - * @buffer: pointer to the end of the buffer - * @buflen: pointer to buffer length - * - * The function will first try to write out the pathname without taking any - * lock other than the RCU read lock to make sure that dentries won't go away. - * It only checks the sequence number of the global rename_lock as any change - * in the dentry's d_seq will be preceded by changes in the rename_lock - * sequence number. If the sequence number had been changed, it will restart - * the whole pathname back-tracing sequence again by taking the rename_lock. - * In this case, there is no need to take the RCU read lock as the recursive - * parent pointer references will keep the dentry chain alive as long as no - * rename operation is performed. - */ -static int prepend_path(const struct path *path, - const struct path *root, - char **buffer, int *buflen) -{ - struct dentry *dentry; - struct vfsmount *vfsmnt; - struct mount *mnt; - int error = 0; - unsigned seq, m_seq = 0; - char *bptr; - int blen; - - rcu_read_lock(); -restart_mnt: - read_seqbegin_or_lock(&mount_lock, &m_seq); - seq = 0; - rcu_read_lock(); -restart: - bptr = *buffer; - blen = *buflen; - error = 0; - dentry = path->dentry; - vfsmnt = path->mnt; - mnt = real_mount(vfsmnt); - read_seqbegin_or_lock(&rename_lock, &seq); - while (dentry != root->dentry || vfsmnt != root->mnt) { - struct dentry * parent; - - if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { - struct mount *parent = READ_ONCE(mnt->mnt_parent); - /* Escaped? */ - if (dentry != vfsmnt->mnt_root) { - bptr = *buffer; - blen = *buflen; - error = 3; - break; - } - /* Global root? */ - if (mnt != parent) { - dentry = READ_ONCE(mnt->mnt_mountpoint); - mnt = parent; - vfsmnt = &mnt->mnt; - continue; - } - if (!error) - error = is_mounted(vfsmnt) ? 1 : 2; - break; - } - parent = dentry->d_parent; - prefetch(parent); - error = prepend_name(&bptr, &blen, &dentry->d_name); - if (error) - break; - - dentry = parent; - } - if (!(seq & 1)) - rcu_read_unlock(); - if (need_seqretry(&rename_lock, seq)) { - seq = 1; - goto restart; - } - done_seqretry(&rename_lock, seq); - - if (!(m_seq & 1)) - rcu_read_unlock(); - if (need_seqretry(&mount_lock, m_seq)) { - m_seq = 1; - goto restart_mnt; - } - done_seqretry(&mount_lock, m_seq); - - if (error >= 0 && bptr == *buffer) { - if (--blen < 0) - error = -ENAMETOOLONG; - else - *--bptr = '/'; - } - *buffer = bptr; - *buflen = blen; - return error; -} - -/** - * __d_path - return the path of a dentry - * @path: the dentry/vfsmount to report - * @root: root vfsmnt/dentry - * @buf: buffer to return value in - * @buflen: buffer length - * - * Convert a dentry into an ASCII path name. - * - * Returns a pointer into the buffer or an error code if the - * path was too long. - * - * "buflen" should be positive. - * - * If the path is not reachable from the supplied root, return %NULL. - */ -char *__d_path(const struct path *path, - const struct path *root, - char *buf, int buflen) -{ - char *res = buf + buflen; - int error; - - prepend(&res, &buflen, "\0", 1); - error = prepend_path(path, root, &res, &buflen); - - if (error < 0) - return ERR_PTR(error); - if (error > 0) - return NULL; - return res; -} - -char *d_absolute_path(const struct path *path, - char *buf, int buflen) -{ - struct path root = {}; - char *res = buf + buflen; - int error; - - prepend(&res, &buflen, "\0", 1); - error = prepend_path(path, &root, &res, &buflen); - - if (error > 1) - error = -EINVAL; - if (error < 0) - return ERR_PTR(error); - return res; -} - -/* - * same as __d_path but appends "(deleted)" for unlinked files. - */ -static int path_with_deleted(const struct path *path, - const struct path *root, - char **buf, int *buflen) -{ - prepend(buf, buflen, "\0", 1); - if (d_unlinked(path->dentry)) { - int error = prepend(buf, buflen, " (deleted)", 10); - if (error) - return error; - } - - return prepend_path(path, root, buf, buflen); -} - -static int prepend_unreachable(char **buffer, int *buflen) -{ - return prepend(buffer, buflen, "(unreachable)", 13); -} - -static void get_fs_root_rcu(struct fs_struct *fs, struct path *root) -{ - unsigned seq; - - do { - seq = read_seqcount_begin(&fs->seq); - *root = fs->root; - } while (read_seqcount_retry(&fs->seq, seq)); -} - -/** - * d_path - return the path of a dentry - * @path: path to report - * @buf: buffer to return value in - * @buflen: buffer length - * - * Convert a dentry into an ASCII path name. If the entry has been deleted - * the string " (deleted)" is appended. Note that this is ambiguous. - * - * Returns a pointer into the buffer or an error code if the path was - * too long. Note: Callers should use the returned pointer, not the passed - * in buffer, to use the name! The implementation often starts at an offset - * into the buffer, and may leave 0 bytes at the start. - * - * "buflen" should be positive. - */ -char *d_path(const struct path *path, char *buf, int buflen) -{ - char *res = buf + buflen; - struct path root; - int error; - - /* - * We have various synthetic filesystems that never get mounted. On - * these filesystems dentries are never used for lookup purposes, and - * thus don't need to be hashed. They also don't need a name until a - * user wants to identify the object in /proc/pid/fd/. The little hack - * below allows us to generate a name for these objects on demand: - * - * Some pseudo inodes are mountable. When they are mounted - * path->dentry == path->mnt->mnt_root. In that case don't call d_dname - * and instead have d_path return the mounted path. - */ - if (path->dentry->d_op && path->dentry->d_op->d_dname && - (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root)) - return path->dentry->d_op->d_dname(path->dentry, buf, buflen); - - rcu_read_lock(); - get_fs_root_rcu(current->fs, &root); - error = path_with_deleted(path, &root, &res, &buflen); - rcu_read_unlock(); - - if (error < 0) - res = ERR_PTR(error); - return res; -} -EXPORT_SYMBOL(d_path); - -/* - * Helper function for dentry_operations.d_dname() members - */ -char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen, - const char *fmt, ...) -{ - va_list args; - char temp[64]; - int sz; - - va_start(args, fmt); - sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1; - va_end(args); - - if (sz > sizeof(temp) || sz > buflen) - return ERR_PTR(-ENAMETOOLONG); - - buffer += buflen - sz; - return memcpy(buffer, temp, sz); -} - -char *simple_dname(struct dentry *dentry, char *buffer, int buflen) -{ - char *end = buffer + buflen; - /* these dentries are never renamed, so d_lock is not needed */ - if (prepend(&end, &buflen, " (deleted)", 11) || - prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) || - prepend(&end, &buflen, "/", 1)) - end = ERR_PTR(-ENAMETOOLONG); - return end; -} -EXPORT_SYMBOL(simple_dname); - -/* - * Write full pathname from the root of the filesystem into the buffer. - */ -static char *__dentry_path(struct dentry *d, char *buf, int buflen) -{ - struct dentry *dentry; - char *end, *retval; - int len, seq = 0; - int error = 0; - - if (buflen < 2) - goto Elong; - - rcu_read_lock(); -restart: - dentry = d; - end = buf + buflen; - len = buflen; - prepend(&end, &len, "\0", 1); - /* Get '/' right */ - retval = end-1; - *retval = '/'; - read_seqbegin_or_lock(&rename_lock, &seq); - while (!IS_ROOT(dentry)) { - struct dentry *parent = dentry->d_parent; - - prefetch(parent); - error = prepend_name(&end, &len, &dentry->d_name); - if (error) - break; - - retval = end; - dentry = parent; - } - if (!(seq & 1)) - rcu_read_unlock(); - if (need_seqretry(&rename_lock, seq)) { - seq = 1; - goto restart; - } - done_seqretry(&rename_lock, seq); - if (error) - goto Elong; - return retval; -Elong: - return ERR_PTR(-ENAMETOOLONG); -} - -char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen) -{ - return __dentry_path(dentry, buf, buflen); -} -EXPORT_SYMBOL(dentry_path_raw); - -char *dentry_path(struct dentry *dentry, char *buf, int buflen) -{ - char *p = NULL; - char *retval; - - if (d_unlinked(dentry)) { - p = buf + buflen; - if (prepend(&p, &buflen, "//deleted", 10) != 0) - goto Elong; - buflen++; - } - retval = __dentry_path(dentry, buf, buflen); - if (!IS_ERR(retval) && p) - *p = '/'; /* restore '/' overriden with '\0' */ - return retval; -Elong: - return ERR_PTR(-ENAMETOOLONG); -} - -static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root, - struct path *pwd) -{ - unsigned seq; - - do { - seq = read_seqcount_begin(&fs->seq); - *root = fs->root; - *pwd = fs->pwd; - } while (read_seqcount_retry(&fs->seq, seq)); -} - -/* - * NOTE! The user-level library version returns a - * character pointer. The kernel system call just - * returns the length of the buffer filled (which - * includes the ending '\0' character), or a negative - * error value. So libc would do something like - * - * char *getcwd(char * buf, size_t size) - * { - * int retval; - * - * retval = sys_getcwd(buf, size); - * if (retval >= 0) - * return buf; - * errno = -retval; - * return NULL; - * } - */ -SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) -{ - int error; - struct path pwd, root; - char *page = __getname(); - - if (!page) - return -ENOMEM; - - rcu_read_lock(); - get_fs_root_and_pwd_rcu(current->fs, &root, &pwd); - - error = -ENOENT; - if (!d_unlinked(pwd.dentry)) { - unsigned long len; - char *cwd = page + PATH_MAX; - int buflen = PATH_MAX; - - prepend(&cwd, &buflen, "\0", 1); - error = prepend_path(&pwd, &root, &cwd, &buflen); - rcu_read_unlock(); - - if (error < 0) - goto out; - - /* Unreachable from current root */ - if (error > 0) { - error = prepend_unreachable(&cwd, &buflen); - if (error) - goto out; - } - - error = -ERANGE; - len = PATH_MAX + page - cwd; - if (len <= size) { - error = len; - if (copy_to_user(buf, cwd, len)) - error = -EFAULT; - } - } else { - rcu_read_unlock(); - } - -out: - __putname(page); - return error; -} - /* * Test whether new_dentry is a subdirectory of old_dentry. * |