Messages in this thread | | | Subject | Re: [PATCH 31/34] vfs: syscall: Add fspick() to select a superblock for reconfiguration [ver #12] | From | Alan Jenkins <> | Date | Sat, 13 Oct 2018 10:45:01 +0100 |
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On 13/10/2018 07:11, Al Viro wrote: > On Fri, Oct 12, 2018 at 03:49:50PM +0100, Alan Jenkins wrote: >>> +SYSCALL_DEFINE3(fspick, int, dfd, const char __user *, path, unsigned int, flags) >>> +{ >>> + struct fs_context *fc; >>> + struct path target; >>> + unsigned int lookup_flags; >>> + int ret; >>> + >>> + if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN)) >>> + return -EPERM; >> >> This seems to accept basically any mount. Specifically: are you sure it's >> OK to return a handle to a SB_NO_USER superblock? > Umm... As long as we don't try to do pathname resolution from its ->s_root, > shouldn't be a problem and I don't see anything that would do that. I might've > missed something, but...
Sorry, I guess SB_NOUSER was the wrong word. I was trying find if anything stopped things like
int memfd = memfd_create("foo", 0); int fsfd = fspick(memfd, "", FSPICK_EMPTY_PATH);
fsconfig(fsfd, FSCONFIG_SET_FLAG, "ro", NULL, 0); fsconfig(fsfd, FSCONFIG_SET_STRING, "size", "100M", 0); fsconfig(fsfd, FSCONFIG_CMD_RECONFIGURE, NULL, NULL, 0);
So far I'm getting -EBUSY if I try to apply the "ro", -EINVAL if I try to apply the "size=100M". But if I don't apply either, then FSCONFIG_CMD_RECONFIGURE succeeds.
It seems worrying that it might let me set options on shm_mnt. Or at least letting me get as far as the -EBUSY check for the "ro" superblock flag.
I'm not sure why I'm getting the -EINVAL setting the "size" option. But it would be much more reassuring if I was getting -EPERM :-).
Alan
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