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author | Linus Torvalds <torvalds@linux-foundation.org> | 2021-07-03 11:23:40 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-07-03 11:23:40 -0700 |
commit | f92a322a63517a798f2da57d56b483a6ae8f45a1 (patch) | |
tree | bc869be0ef708766727f92a6345912de91d6d54e | |
parent | 757fa80f4edca010769f3f8d116c19c85f27e817 (diff) | |
parent | e4b275531887fef7f7d8a7284bfc32f0fbbd4208 (diff) | |
download | linux-f92a322a63517a798f2da57d56b483a6ae8f45a1.tar.gz linux-f92a322a63517a798f2da57d56b483a6ae8f45a1.tar.bz2 linux-f92a322a63517a798f2da57d56b483a6ae8f45a1.zip |
Merge branch 'work.d_path' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs d_path() updates from Al Viro:
"d_path.c refactoring"
* 'work.d_path' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
getcwd(2): clean up error handling
d_path: prepend_path() is unlikely to return non-zero
d_path: prepend_path(): lift the inner loop into a new helper
d_path: prepend_path(): lift resetting b in case when we'd return 3 out of loop
d_path: prepend_path(): get rid of vfsmnt
d_path: introduce struct prepend_buffer
d_path: make prepend_name() boolean
d_path: lift -ENAMETOOLONG handling into callers of prepend_path()
d_path: don't bother with return value of prepend()
getcwd(2): saner logics around prepend_path() call
d_path: get rid of path_with_deleted()
d_path: regularize handling of root dentry in __dentry_path()
d_path: saner calling conventions for __dentry_path()
d_path: "\0" is {0,0}, not {0}
-rw-r--r-- | fs/d_path.c | 324 |
1 files changed, 133 insertions, 191 deletions
diff --git a/fs/d_path.c b/fs/d_path.c index 270d62133996..23a53f7b5c71 100644 --- a/fs/d_path.c +++ b/fs/d_path.c @@ -8,14 +8,27 @@ #include <linux/prefetch.h> #include "mount.h" -static int prepend(char **buffer, int *buflen, const char *str, int namelen) +struct prepend_buffer { + char *buf; + int len; +}; +#define DECLARE_BUFFER(__name, __buf, __len) \ + struct prepend_buffer __name = {.buf = __buf + __len, .len = __len} + +static char *extract_string(struct prepend_buffer *p) { - *buflen -= namelen; - if (*buflen < 0) - return -ENAMETOOLONG; - *buffer -= namelen; - memcpy(*buffer, str, namelen); - return 0; + if (likely(p->len >= 0)) + return p->buf; + return ERR_PTR(-ENAMETOOLONG); +} + +static void prepend(struct prepend_buffer *p, const char *str, int namelen) +{ + p->len -= namelen; + if (likely(p->len >= 0)) { + p->buf -= namelen; + memcpy(p->buf, str, namelen); + } } /** @@ -35,22 +48,58 @@ static int prepend(char **buffer, int *buflen, const char *str, int namelen) * * 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) +static bool prepend_name(struct prepend_buffer *p, const struct qstr *name) { const char *dname = smp_load_acquire(&name->name); /* ^^^ */ u32 dlen = READ_ONCE(name->len); - char *p; + char *s; - *buflen -= dlen + 1; - if (*buflen < 0) - return -ENAMETOOLONG; - p = *buffer -= dlen + 1; - *p++ = '/'; + p->len -= dlen + 1; + if (unlikely(p->len < 0)) + return false; + s = p->buf -= dlen + 1; + *s++ = '/'; while (dlen--) { char c = *dname++; if (!c) break; - *p++ = c; + *s++ = c; + } + return true; +} + +static int __prepend_path(const struct dentry *dentry, const struct mount *mnt, + const struct path *root, struct prepend_buffer *p) +{ + while (dentry != root->dentry || &mnt->mnt != root->mnt) { + const struct dentry *parent = READ_ONCE(dentry->d_parent); + + if (dentry == mnt->mnt.mnt_root) { + struct mount *m = READ_ONCE(mnt->mnt_parent); + struct mnt_namespace *mnt_ns; + + if (likely(mnt != m)) { + dentry = READ_ONCE(mnt->mnt_mountpoint); + mnt = m; + continue; + } + /* Global root */ + mnt_ns = READ_ONCE(mnt->mnt_ns); + /* open-coded is_mounted() to use local mnt_ns */ + if (!IS_ERR_OR_NULL(mnt_ns) && !is_anon_ns(mnt_ns)) + return 1; // absolute root + else + return 2; // detached or not attached yet + } + + if (unlikely(dentry == parent)) + /* Escaped? */ + return 3; + + prefetch(parent); + if (!prepend_name(p, &dentry->d_name)) + break; + dentry = parent; } return 0; } @@ -74,15 +123,11 @@ static int prepend_name(char **buffer, int *buflen, const struct qstr *name) */ static int prepend_path(const struct path *path, const struct path *root, - char **buffer, int *buflen) + struct prepend_buffer *p) { - struct dentry *dentry; - struct vfsmount *vfsmnt; - struct mount *mnt; - int error = 0; unsigned seq, m_seq = 0; - char *bptr; - int blen; + struct prepend_buffer b; + int error; rcu_read_lock(); restart_mnt: @@ -90,50 +135,9 @@ restart_mnt: seq = 0; rcu_read_lock(); restart: - bptr = *buffer; - blen = *buflen; - error = 0; - dentry = path->dentry; - vfsmnt = path->mnt; - mnt = real_mount(vfsmnt); + b = *p; 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); - struct mnt_namespace *mnt_ns; - - /* 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; - } - mnt_ns = READ_ONCE(mnt->mnt_ns); - /* open-coded is_mounted() to use local mnt_ns */ - if (!IS_ERR_OR_NULL(mnt_ns) && !is_anon_ns(mnt_ns)) - error = 1; // absolute root - else - error = 2; // detached or not attached yet - break; - } - parent = dentry->d_parent; - prefetch(parent); - error = prepend_name(&bptr, &blen, &dentry->d_name); - if (error) - break; - - dentry = parent; - } + error = __prepend_path(path->dentry, real_mount(path->mnt), root, &b); if (!(seq & 1)) rcu_read_unlock(); if (need_seqretry(&rename_lock, seq)) { @@ -150,14 +154,13 @@ restart: } done_seqretry(&mount_lock, m_seq); - if (error >= 0 && bptr == *buffer) { - if (--blen < 0) - error = -ENAMETOOLONG; - else - *--bptr = '/'; - } - *buffer = bptr; - *buflen = blen; + if (unlikely(error == 3)) + b = *p; + + if (b.len == p->len) + prepend(&b, "/", 1); + + *p = b; return error; } @@ -181,56 +184,24 @@ 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); + DECLARE_BUFFER(b, buf, buflen); - if (error < 0) - return ERR_PTR(error); - if (error > 0) + prepend(&b, "", 1); + if (unlikely(prepend_path(path, root, &b) > 0)) return NULL; - return res; + return extract_string(&b); } 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); -} + DECLARE_BUFFER(b, buf, buflen); -static int prepend_unreachable(char **buffer, int *buflen) -{ - return prepend(buffer, buflen, "(unreachable)", 13); + prepend(&b, "", 1); + if (unlikely(prepend_path(path, &root, &b) > 1)) + return ERR_PTR(-EINVAL); + return extract_string(&b); } static void get_fs_root_rcu(struct fs_struct *fs, struct path *root) @@ -261,9 +232,8 @@ static void get_fs_root_rcu(struct fs_struct *fs, struct path *root) */ char *d_path(const struct path *path, char *buf, int buflen) { - char *res = buf + buflen; + DECLARE_BUFFER(b, buf, buflen); struct path root; - int error; /* * We have various synthetic filesystems that never get mounted. On @@ -282,12 +252,14 @@ char *d_path(const struct path *path, char *buf, int buflen) rcu_read_lock(); get_fs_root_rcu(current->fs, &root); - error = path_with_deleted(path, &root, &res, &buflen); + if (unlikely(d_unlinked(path->dentry))) + prepend(&b, " (deleted)", 11); + else + prepend(&b, "", 1); + prepend_path(path, &root, &b); rcu_read_unlock(); - if (error < 0) - res = ERR_PTR(error); - return res; + return extract_string(&b); } EXPORT_SYMBOL(d_path); @@ -314,47 +286,34 @@ char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen, char *simple_dname(struct dentry *dentry, char *buffer, int buflen) { - char *end = buffer + buflen; + DECLARE_BUFFER(b, 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; + prepend(&b, " (deleted)", 11); + prepend(&b, dentry->d_name.name, dentry->d_name.len); + prepend(&b, "/", 1); + return extract_string(&b); } /* * Write full pathname from the root of the filesystem into the buffer. */ -static char *__dentry_path(const struct dentry *d, char *buf, int buflen) +static char *__dentry_path(const struct dentry *d, struct prepend_buffer *p) { const struct dentry *dentry; - char *end, *retval; - int len, seq = 0; - int error = 0; - - if (buflen < 2) - goto Elong; + struct prepend_buffer b; + int seq = 0; rcu_read_lock(); restart: dentry = d; - end = buf + buflen; - len = buflen; - prepend(&end, &len, "\0", 1); - /* Get '/' right */ - retval = end-1; - *retval = '/'; + b = *p; read_seqbegin_or_lock(&rename_lock, &seq); while (!IS_ROOT(dentry)) { const struct dentry *parent = dentry->d_parent; prefetch(parent); - error = prepend_name(&end, &len, &dentry->d_name); - if (error) + if (!prepend_name(&b, &dentry->d_name)) break; - - retval = end; dentry = parent; } if (!(seq & 1)) @@ -364,36 +323,29 @@ restart: goto restart; } done_seqretry(&rename_lock, seq); - if (error) - goto Elong; - return retval; -Elong: - return ERR_PTR(-ENAMETOOLONG); + if (b.len == p->len) + prepend(&b, "/", 1); + return extract_string(&b); } char *dentry_path_raw(const struct dentry *dentry, char *buf, int buflen) { - return __dentry_path(dentry, buf, buflen); + DECLARE_BUFFER(b, buf, buflen); + + prepend(&b, "", 1); + return __dentry_path(dentry, &b); } EXPORT_SYMBOL(dentry_path_raw); char *dentry_path(const 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); + DECLARE_BUFFER(b, buf, buflen); + + if (unlikely(d_unlinked(dentry))) + prepend(&b, "//deleted", 10); + else + prepend(&b, "", 1); + return __dentry_path(dentry, &b); } static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root, @@ -438,38 +390,28 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size) 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); + if (unlikely(d_unlinked(pwd.dentry))) { rcu_read_unlock(); + error = -ENOENT; + } else { + unsigned len; + DECLARE_BUFFER(b, page, PATH_MAX); - if (error < 0) - goto out; - - /* Unreachable from current root */ - if (error > 0) { - error = prepend_unreachable(&cwd, &buflen); - if (error) - goto out; - } + prepend(&b, "", 1); + if (unlikely(prepend_path(&pwd, &root, &b) > 0)) + prepend(&b, "(unreachable)", 13); + rcu_read_unlock(); - error = -ERANGE; - len = PATH_MAX + page - cwd; - if (len <= size) { + len = PATH_MAX - b.len; + if (unlikely(len > PATH_MAX)) + error = -ENAMETOOLONG; + else if (unlikely(len > size)) + error = -ERANGE; + else if (copy_to_user(buf, b.buf, len)) + error = -EFAULT; + else error = len; - if (copy_to_user(buf, cwd, len)) - error = -EFAULT; - } - } else { - rcu_read_unlock(); } - -out: __putname(page); return error; } |