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Re: vzctl: race condition at open("/sbin/init") [message #47917 is a reply to message #47277]

Tue, 18 September 2012 15:09

kir
Messages: 1645
Registered: August 2005
Location: Moscow, Russia

Senior Member

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,
>

Kir Kolyshkin

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[Message index]

		vzctl: race condition at open("/sbin/init") By: Vasily Kulikov on Wed, 25 July 2012 19:07
		Re: vzctl: race condition at open("/sbin/init") By: kir on Tue, 18 September 2012 15:09
		Re: vzctl: race condition at open("/sbin/init") By: Vasily Kulikov on Tue, 18 September 2012 20:12

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