Messages in this thread | | | Date | Tue, 30 Jul 2013 16:16:51 -0700 | From | Zach Levis <> | Subject | Re: [PATCH 2/3] fs/binfmts: Better handling of binfmt loops |
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Quoting Andrew Morton <akpm@linux-foundation.org>:
> On Thu, 25 Jul 2013 08:40:44 -0700 Zach Levis <zml@linux.vnet.ibm.com> wrote: > >> With these changes, when a binfmt loop is encountered, >> the ELOOP will propogate back to the 0 depth. At this point the >> argv and argc values will be reset to what they were originally and an >> attempt is made to continue with the following binfmt handlers. > > hm, why? What problem does this fix? What value does the change offer > to our users?
This is used when the binfmt_misc,script,etc options are configured in a way that would previously prevent executables from launching that could be executed with a different binfmt but don't because of a loop in a prior binfmt.
Example: a qemu is configured to run 64-bit ELFs on an otherwise 32-bit system. The system's owner switches to running with 64-bit executables, but forgets to disable the binfmt_misc option that redirects 64bit ELFs to qemu. Since the qemu executable is a 64-bit ELF now, binfmt_misc keeps on matching it with the qemu rule, preventing the execution of any 64-bit binary.
With this patch, an error is printed and search_binary_handler() continues on to the next handler, allowing the original executable to run normally so the user can (hopefully) fix their misconfiguration more easily.
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