From: Linus Torvalds <torvalds@linux-foundation.org>
To: Aleksa Sarai <cyphar@cyphar.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Jeff Layton <jlayton@kernel.org>,
"J. Bruce Fields" <bfields@fieldses.org>,
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Subject: Re: [PATCH v14 2/6] namei: LOOKUP_IN_ROOT: chroot-like path resolution
Date: Thu, 10 Oct 2019 10:07:32 -0700 [thread overview]
Message-ID: <CAHk-=wh8L50f31vW8BwRUXhLiq3eoCQ3tg8ER4Yp2dzuU1w5rQ@mail.gmail.com> (raw)
In-Reply-To: <20191010054140.8483-3-cyphar@cyphar.com>
On Wed, Oct 9, 2019 at 10:42 PM Aleksa Sarai <cyphar@cyphar.com> wrote:
>
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -2277,6 +2277,11 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
>
> nd->m_seq = read_seqbegin(&mount_lock);
>
> + /* LOOKUP_IN_ROOT treats absolute paths as being relative-to-dirfd. */
> + if (flags & LOOKUP_IN_ROOT)
> + while (*s == '/')
> + s++;
> +
> /* Figure out the starting path and root (if needed). */
> if (*s == '/') {
> error = nd_jump_root(nd);
Hmm. Wouldn't this make more sense all inside the if (*s =- '/') test?
That way if would be where we check for "should we start at the root",
which seems to make more sense conceptually.
That test for '/' currently has a "} else if (..)", but that's
pointless since it ends with a "return" anyway. So the "else" logic is
just noise.
And if you get rid of the unnecessary else, moving the LOOKUP_IN_ROOT
inside the if-statement works fine.
So this could be something like
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2194,11 +2196,19 @@ static const char *path_init(struct
nameidata *nd, unsigned flags)
nd->m_seq = read_seqbegin(&mount_lock);
if (*s == '/') {
- set_root(nd);
- if (likely(!nd_jump_root(nd)))
- return s;
- return ERR_PTR(-ECHILD);
- } else if (nd->dfd == AT_FDCWD) {
+ /* LOOKUP_IN_ROOT treats absolute paths as being
relative-to-dirfd. */
+ if (!(flags & LOOKUP_IN_ROOT)) {
+ set_root(nd);
+ if (likely(!nd_jump_root(nd)))
+ return s;
+ return ERR_PTR(-ECHILD);
+ }
+
+ /* Skip initial '/' for LOOKUP_IN_ROOT */
+ do { s++; } while (*s == '/');
+ }
+
+ if (nd->dfd == AT_FDCWD) {
if (flags & LOOKUP_RCU) {
struct fs_struct *fs = current->fs;
unsigned seq;
instead. The patch ends up slightly bigger (due to the re-indentation)
but now it handles all the "start at root" in the same place. Doesn't
that make sense?
Linus
next prev parent reply other threads:[~2019-10-10 17:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-10 5:41 [PATCH v14 0/6] open: introduce openat2(2) syscall Aleksa Sarai
2019-10-10 5:41 ` [PATCH v14 1/6] namei: O_BENEATH-style resolution restriction flags Aleksa Sarai
2019-10-10 5:41 ` [PATCH v14 2/6] namei: LOOKUP_IN_ROOT: chroot-like path resolution Aleksa Sarai
2019-10-10 17:07 ` Linus Torvalds [this message]
2019-10-12 4:08 ` Aleksa Sarai
2019-10-12 4:15 ` Aleksa Sarai
2019-10-24 7:06 ` Aleksa Sarai
2019-10-10 5:41 ` [PATCH v14 3/6] namei: permit ".." resolution with LOOKUP_{IN_ROOT,BENEATH} Aleksa Sarai
2019-10-10 5:41 ` [PATCH v14 4/6] open: introduce openat2(2) syscall Aleksa Sarai
2019-10-10 5:41 ` [PATCH v14 5/6] selftests: add openat2(2) selftests Aleksa Sarai
2019-10-10 5:41 ` [PATCH v14 6/6] Documentation: path-lookup: mention LOOKUP_MAGICLINK_JUMPED Aleksa Sarai
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