linux-kernel - Re: Executable loading issues with erofs on arm?

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Message-ID: <452a2155-ab3b-43d1-8783-0f1db13a675f@siemens.com>
Date: Tue, 8 Jul 2025 14:43:58 +0200
From: Jan Kiszka <jan.kiszka@...mens.com>
To: Gao Xiang <xiang@...nel.org>, Chao Yu <chao@...nel.org>,
 linux-erofs@...ts.ozlabs.org
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Executable loading issues with erofs on arm?

On 08.07.25 14:41, Jan Kiszka wrote:
> Hi all,
> 
> for some days, I'm trying to understand if we have an integration issue
> with erofs or rather some upstream bug. After playing with various
> parameters, it rather looks like the latter:
> 
> $ ls -l erofs-dir/
> total 132
> -rwxr-xr-x 1 1000 users 132868 Jul  8 10:50 dash
> (from Debian bookworm)
> $ mkfs.erofs -z lz4hc erofs.img erofs-dir/
> mkfs.erofs 1.8.6 (trixie version, but same happens with bookworm 1.5)
> Build completed.
> ------
> Filesystem UUID: aae0b2f0-4ee4-4850-af49-3c1aad7fa30c
> Filesystem total blocks: 17 (of 4096-byte blocks)
> Filesystem total inodes: 2
> Filesystem total metadata blocks: 1
> Filesystem total deduplicated bytes (of source files): 0
> 
> Now I have 6.15-rc5 and a defconfig-close setting for the 32-bit ARM
> target BeagleBone Black. When booting into init=/bin/sh, then running
> 
> # mount -t erofs /dev/mmcblk0p1 /mnt
> erofs (device mmcblk0p1): mounted with root inode @ nid 36.
> # /mnt/dash
> Segmentation fault
> 
> I once also got this:
> 
> Alignment trap: not handling instruction 2b00 at [<004debc0>]
> 8<--- cut here ---
> Unhandled fault: alignment exception (0x001) at 0x000004d9
> [000004d9] *pgd=00000000
> Bus error
> 
> All is fine if I
>  - run the command once more
>  - dump the file first (cat /mnt/dash > /dev/null; /mnt/dash)

Forgot to mention: That first dump when done via md5sum or so actually
gives the right checksum. So pure reading of the binary is also ok, just
trying to load it for execution fails on the first attempt.

Jan

>  - boot a full Debian system and then mount & run the command
>  - do not compress erofs
> 
> Also broken is -z zstd, so the decompression algorithm itself should not
> be the reason. I furthermore tested older kernels as well, namely
> stable-derived 6.1-cip and 6.12-cip, and those are equally affected.
> 
> Any ideas? I have CONFIG_EROFS_FS_DEBUG=y, but that does not trigger
> anything. Is there anything I could instrument?
> 
> Jan
> 

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