Messages in this thread | | | Subject | Potential bug in fs/binfmt_elf.c? | From | Mike Hearn <> | Date | Fri, 05 Mar 2004 17:38:01 +0000 |
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Hi,
I believe there is a problem in fs/binfmt_elf.c, around line 700 (kernel 2.6.1)
When mapping a nobits PT_LOAD segment with a memsize > filesize, the kernel calls set_brk (which in turns calls do_brk) to map and clear the area, but this discards access permissons on the mapping leading to rwx protection. This causes a load failure on systems where the VM cannot reserve swap space for the segment, unless overcommit is active (on many systems it's not on by default).
I don't know this code well, but it seems that this discarding of access permissions on the unlikely codepath is incorrect. I filed bug #2255 [1] on it.
Could somebody who understands the ELF loading code please check to see if this is a bug, and if so produce a patch?
The ability to define a new (large) ELF section which isn't backed by swap space nor disk space and that will be mapped to a specific VMA range is needed by Wine to reserve the PE load area.
Currently the fact that the section is always mapped rwx despite being marked read-only in the binary prevents us from using this as a solution to the problems caused by exec-shield/prelink, meaning the only solution is to bootstrap the ELF interpreter ourselves from a statically linked binary. Clearly we'd rather not do that.
Thanks to pageexec@freemail.hu for bringing the matter to my attention.
Your assistance is appreciated, thanks -mike
[1] http://bugzilla.kernel.org/show_bug.cgi?id=2255
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