Message-ID: <e2b90c55-1a4a-4cf1-2dc7-2b2a4dc7d168@leemhuis.info>
Date:   Thu, 31 Mar 2022 08:17:30 +0200
From:   Thorsten Leemhuis <regressions@...mhuis.info>
To:     "H.J. Lu" <hjl.tools@...il.com>
Cc:     "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Chris Kennelly <ckennelly@...gle.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Song Liu <songliubraving@...com>,
        David Rientjes <rientjes@...gle.com>,
        Ian Rogers <irogers@...gle.com>,
        Hugh Dickins <hughd@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Sandeep Patil <sspatil@...gle.com>,
        Fangrui Song <maskray@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Shuah Khan <shuah@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Bug 215734 - shared object loaded very low in memory ARM 32bit with
 kernel 5.17.0

Hi, this is your Linux kernel regression tracker.

I noticed a regression report in bugzilla.kernel.org that afaics nobody
acted upon since it was reported about a week ago, that's why I decided
to forward it to the lists and all people that seemed to be relevant
here. Note, this is the second regression report referencin a commit
from H.J. Lu as culprit (9630f0d60fec ("fs/binfmt_elf: use PT_LOAD
p_align values for static PIE")). I forwarded the first one on Monday
already, but seems nothing happened:
https://lore.kernel.org/all/cb5b81bd-9882-e5dc-cd22-54bdbaaefbbc@leemhuis.info/

Anyway, to get back to the latest report. To quote from
https://bugzilla.kernel.org/show_bug.cgi?id=215734 :

>  Jan Palus 2022-03-24 10:17:02 UTC
> 
> This is a followup to https://sourceware.org/bugzilla/show_bug.cgi?id=28990 where ld.so --verify segfault was reported on binaries > 4MB.
> 
> It appears that starting with kernel 5.17.0 shared object is loaded in the begging of address space at least on 32-bit ARM:
> 
> /proc/<pid>/maps just before mmap (5.17):
> 00400000-00429000 r-xp 00000000 b3:02 393320     /lib/ld-linux-armhf.so.3
> 00439000-0043c000 rw-p 00029000 b3:02 393320     /lib/ld-linux-armhf.so.3
> 76ffd000-76ffe000 r-xp 00000000 00:00 0          [sigpage]
> 76ffe000-76fff000 r--p 00000000 00:00 0          [vvar]
> 76fff000-77000000 r-xp 00000000 00:00 0          [vdso]
> 7efdf000-7f000000 rw-p 00000000 00:00 0          [stack]
> ffff0000-ffff1000 r-xp 00000000 00:00 0          [vectors]
> 
> causing segfaults when mmaping large binaries at fixed address 0x10000 (ie done by ld.so --verify used by ldd).
> 
> By comparison it is not the case for kernel 5.16.8:
> 
> /proc/<pid>/maps just before mmap (5.16):
> 76fc4000-76fed000 r-xp 00000000 b3:02 393320     /lib/ld-linux-armhf.so.3
> 76ffa000-76ffb000 r-xp 00000000 00:00 0          [sigpage]
> 76ffb000-76ffc000 r--p 00000000 00:00 0          [vvar]
> 76ffc000-76ffd000 r-xp 00000000 00:00 0          [vdso]
> 76ffd000-77000000 rw-p 00029000 b3:02 393320     /lib/ld-linux-armhf.so.3
> 7efdf000-7f000000 rw-p 00000000 00:00 0          [stack]
> ffff0000-ffff1000 r-xp 00000000 00:00 0          [vectors]
> 
> [reply] [−] Comment 1 Jan Palus 2022-03-29 22:14:12 UTC
> 
> First bad commit appears to be:
> 
> From: "H.J. Lu" <hjl.tools@...il.com>
> Date: Wed, 19 Jan 2022 18:09:40 -0800
> Subject: fs/binfmt_elf: use PT_LOAD p_align values for static PIE
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9630f0d60fec5fbcaa4435a66f75df1dc9704b66
> 

Could somebody take a look into this? Or was this discussed somewhere
else already? Or even fixed?


Anyway, to get this tracked:

#regzbot introduced: 9630f0d60fec5fbcaa4435a66f75df1dc9704b6
#regzbot from: Jan Palus <jpalus@...tmail.com>
#regzbot title: shared object loaded very low in memory ARM 32bit
causing segfaults on binaries > 4MB
#regzbot link: https://bugzilla.kernel.org/show_bug.cgi?id=215734

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)

P.S.: As the Linux kernel's regression tracker I'm getting a lot of
reports on my table. I can only look briefly into most of them and lack
knowledge about most of the areas they concern. I thus unfortunately
will sometimes get things wrong or miss something important. I hope
that's not the case here; if you think it is, don't hesitate to tell me
in a public reply, it's in everyone's interest to set the public record
straight.

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