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| author | Michael Kerrisk <mtk.manpages@gmail.com> | 2021-08-12 05:16:42 +0200 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2021-08-12 07:33:53 +0200 |
| commit | 45ea537cf2fc7d9804f510e823a8c340db52f7a4 (patch) | |
| tree | 31e13da15c0aca47c1933156457b4ac00ffc9eb3 | |
| parent | faf2534942862b35b8427f348c01c60d6b8b8944 (diff) | |
| download | man-pages-45ea537cf2fc7d9804f510e823a8c340db52f7a4.tar.gz | |
mount_setattr.2: EXAMPLES: use -1 rather than -EBADF
From email with Christian Braner:
> [1]: In this code "source" is expected to be absolute. If it's not
> absolute we should fail. This can be achieved by passing -1/-EBADF,
> afaict.
D'oh! Okay. I hadn't considered that use case for an invalid dirfd.
(And now I've done some adjustments to openat(2),which contains a
rationale for the *at() functions.)
So, now I understand your purpose, but still the code is obscure,
since
* You use a magic value (-EBADF) rather than (say) -1.
* There's no explanation (comment about) of the fact that you want
to prevent relative pathnames.
So, I've changed the code to use -1, not -EBADF, and I've added some
comments to explain that the intent is to prevent relative pathnames.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
| -rw-r--r-- | man2/mount_setattr.2 | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/man2/mount_setattr.2 b/man2/mount_setattr.2 index 0739624cc1..6ffe5e0099 100644 --- a/man2/mount_setattr.2 +++ b/man2/mount_setattr.2 @@ -961,7 +961,10 @@ main(int argc, char *argv[]) const char *source = argv[optind]; const char *target = argv[optind + 1]; - int fd_tree = open_tree(\-EBADF, source, + /* In the following, \-1 as the \(aqdirfd\(aq argument ensures that + open_tree() fails if \(aqsource\(aq is not an absolute pathname. */ + + int fd_tree = open_tree(\-1, source, OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC | AT_EMPTY_PATH | (recursive ? AT_RECURSIVE : 0)); if (fd_tree == \-1) @@ -980,7 +983,10 @@ main(int argc, char *argv[]) close(fd_userns); - ret = move_mount(fd_tree, "", \-EBADF, target, + /* In the following, \-1 as the \(aqto_dirfd\(aq argument ensures that + open_tree() fails if \(aqtarget\(aq is not an absolute pathname. */ + + ret = move_mount(fd_tree, "", \-1, target, MOVE_MOUNT_F_EMPTY_PATH); if (ret == \-1) exit_log("%m \- Failed to attach mount to %s\en", target); |