Messages in this thread | | | From | Christian Göttsche <> | Date | Fri, 19 Aug 2022 20:05:31 +0200 | Subject | Re: [RFC PATCH] f*xattr: allow O_PATH descriptors |
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On Wed, 22 Jun 2022 at 04:57, Aleksa Sarai <cyphar@cyphar.com> wrote: > > On 2022-06-20, Amir Goldstein <amir73il@gmail.com> wrote: > > To be a reasonable reaction to the currently broken API is > > to either accept the patch as is or request that setxattrat() > > will be added to provide the new functionality. > > Since the current functionality cannot be retroactively disabled as it > is being used already through /proc/self/fd/$n, adding > *xattrat(AT_EMPTY_PATH) doesn't really change what is currently possible > by userspace. > > I would say we should add *xattrat(2) and then we can add an upgrade > mask blocking it (and other operations) later. >
It seems setxattrat() is the preferred way to continue. fsetxattr() would have one advantage though (w.r.t. SELinux):
The steps to label a file are: 1. get the type of the file (via stat(2) family) 2. lookup the desired label from the label database via selabel_lookup(3) 3. assign the retrieved label to the file
The label is sensitive to the file type, e.g.
$ matchpathcon -m file /etc/shadow /etc/shadow system_u:object_r:shadow_t:s0 $ matchpathcon -m lnk_file /etc/shadow /etc/shadow system_u:object_r:etc_t:s0
Using the *at() family the file type could change between step 1. and 3., which operating on an O_PATH file descriptor would prevent.
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