[Devel] vzctl: race condition at open("/sbin/init")

[Kir Kolyshkin]

On 07/25/2012 11:07 PM, Vasily Kulikov wrote:
> Hi,
>
> stat()+open() is not atomic in the code below, so there is a race
> condition.  A container root may change /sbin/init between these calls
> to e.g. FIFO and then make the vzctl's process hang up on read().
>
> I'd add O_NOCTTY to open's flags and change stat() before open() to
> fstat() just after open().

Thanks a lot for reporting!

Does this patch seems sufficient to you?
http://git.openvz.org/?p=vzctl;a=commitdiff;h=7c47a7953

>
>
> vzctl-3.3/src/lib/readelf.c:
>
> int get_arch_from_elf(const char *file)
> {
> ...
> 	if (stat(file, &st)) <<<<<
> 		return -1;
> 	if (!S_ISREG(st.st_mode))
> 		return -1;
> 	fd = open(file, O_RDONLY); <<<<<
> 	if (fd < 0)
> 		return -1;
> 	nbytes = read(fd, (void *) &elf_hdr, sizeof(elf_hdr));
> ...
> }
>
> Thanks,
>