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SubjectRe: System reset on Kernel 2.4.10
On Tue, Oct 02, 2001 at 11:02:28PM +0000, Petr Vandrovec wrote:
> On 2 Oct 01 at 23:52, VDA wrote:
> > V> Straced vmlinux does not reboot.
> > V> Kernel: 2.4.10+ext3+preempt
> >
> > Well... sometimes it reboots too.
> > Once it rebooted ~10 mins after strace (system was at zero load).
> > Also it rebooted after two strace's in succession.
>
> Look at fs/binfmt_elf.c, at line 642 (in -ac2). There is
>
> error = elf_map(....)
>
> but nobody bothers with checking error value, it even tries it
> to use as an offset if stars are in wrong constellation.
> If you could add these lines below the call:
>
> if ((unsigned long)error >= (unsigned long)(-256)) {
> set_fs(old_fs);
> printk(KERN_DEBUG "Something went wrong with elf_map()\n");
> kfree(elf_phdata);
> send_sig(SIGSEGV, current, 0);
> return 0;
> }
>
> and then report results...

Well, I was not able to trigger reboot with unpatched kernel. With
patched one behavior looks same to me, except that elf_map went wrong
is printed by kernel.

I was not able to find where problem could be with unpatched
kernel, but arguments passed to do_brk(), set into mm->start_brk,
{start,end}_code and so on looks very suspicious... But as on my
system it does not crash neither with nor without patch below, I
leave answer on someone else.

Btw, my system is 2.4.10-ac2, SMP PIII, compiled with Debian 2.95.4.
Petr Vandrovec
vandrove@vc.cvut.cz


--- linux/fs/binfmt_elf.c.xx Mon Oct 1 18:34:46 2001
+++ linux/fs/binfmt_elf.c Tue Oct 2 23:04:18 2001
@@ -640,7 +640,13 @@
}

error = elf_map(bprm->file, load_bias + vaddr, elf_ppnt, elf_prot, elf_flags);
-
+ if ((unsigned long)error >= (unsigned long)(-256)) {
+ set_fs(old_fs);
+ printk(KERN_DEBUG "elf_map went wrong\n");
+ kfree(elf_phdata);
+ send_sig(SIGSEGV, current, 0);
+ return 0;
+ }
if (!load_addr_set) {
load_addr_set = 1;
load_addr = (elf_ppnt->p_vaddr - elf_ppnt->p_offset);
-
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