linux-kernel - Re: [PATCH 0/2] apparmor unaligned memory fixes

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Message-ID: <be9c143d-1d5e-4c5b-9078-4a7804489258@gmx.de>
Date: Tue, 18 Nov 2025 13:49:22 +0100
From: Helge Deller <deller@....de>
To: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
 Helge Deller <deller@...nel.org>
Cc: linux-kernel@...r.kernel.org, apparmor@...ts.ubuntu.com,
 John Johansen <john.johansen@...onical.com>,
 linux-security-module@...r.kernel.org
Subject: Re: [PATCH 0/2] apparmor unaligned memory fixes

Hi Adrian,

On 11/18/25 12:43, John Paul Adrian Glaubitz wrote:
> On Tue, 2025-11-18 at 12:09 +0100, Helge Deller wrote:
>> My patch fixed two call sites, but I suspect you see another call site which
>> hasn't been fixed yet.
>>
>> Can you try attached patch? It might indicate the caller of the function and
>> maybe prints the struct name/address which isn't aligned.
>>
>> Helge
>>
>>
>> diff --git a/security/apparmor/match.c b/security/apparmor/match.c
>> index c5a91600842a..b477430c07eb 100644
>> --- a/security/apparmor/match.c
>> +++ b/security/apparmor/match.c
>> @@ -313,6 +313,9 @@ struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
>>   	if (size < sizeof(struct table_set_header))
>>   		goto fail;
>>   
>> +	if (WARN_ON(((unsigned long)data) & (BITS_PER_LONG/8 - 1)))
>> +		pr_warn("dfa blob stream %pS not aligned.\n", data);
>> +
>>   	if (ntohl(*(__be32 *) data) != YYTH_MAGIC)
>>   		goto fail;
> 
> Here is the relevant output with the patch applied:
> 
> [   73.840639] ------------[ cut here ]------------
> [   73.901376] WARNING: CPU: 0 PID: 341 at security/apparmor/match.c:316 aa_dfa_unpack+0x6cc/0x720
> [   74.015867] Modules linked in: binfmt_misc evdev flash sg drm drm_panel_orientation_quirks backlight i2c_core configfs nfnetlink autofs4 ext4 crc16 mbcache jbd2 hid_generic usbhid sr_mod hid cdrom
> sd_mod ata_generic ohci_pci ehci_pci ehci_hcd ohci_hcd pata_ali libata sym53c8xx scsi_transport_spi tg3 scsi_mod usbcore libphy scsi_common mdio_bus usb_common
> [   74.428977] CPU: 0 UID: 0 PID: 341 Comm: apparmor_parser Not tainted 6.18.0-rc6+ #9 NONE
> [   74.536543] Call Trace:
> [   74.568561] [<0000000000434c24>] dump_stack+0x8/0x18
> [   74.633757] [<0000000000476438>] __warn+0xd8/0x100
> [   74.696664] [<00000000004296d4>] warn_slowpath_fmt+0x34/0x74
> [   74.771006] [<00000000008db28c>] aa_dfa_unpack+0x6cc/0x720
> [   74.843062] [<00000000008e643c>] unpack_pdb+0xbc/0x7e0
> [   74.910545] [<00000000008e7740>] unpack_profile+0xbe0/0x1300
> [   74.984888] [<00000000008e82e0>] aa_unpack+0xe0/0x6a0
> [   75.051226] [<00000000008e3ec4>] aa_replace_profiles+0x64/0x1160
> [   75.130144] [<00000000008d4d90>] policy_update+0xf0/0x280
> [   75.201057] [<00000000008d4fc8>] profile_replace+0xa8/0x100
> [   75.274258] [<0000000000766bd0>] vfs_write+0x90/0x420
> [   75.340594] [<00000000007670cc>] ksys_write+0x4c/0xe0
> [   75.406932] [<0000000000767174>] sys_write+0x14/0x40
> [   75.472126] [<0000000000406174>] linux_sparc_syscall+0x34/0x44
> [   75.548802] ---[ end trace 0000000000000000 ]---
> [   75.609503] dfa blob stream 0xfff0000008926b96 not aligned.
> [   75.682695] Kernel unaligned access at TPC[8db2a8] aa_dfa_unpack+0x6e8/0x720

The non-8-byte-aligned address (0xfff0000008926b96) is coming from userspace
(via the write syscall).
Some apparmor userspace tool writes into the apparmor ".replace" virtual file with
a source address which is not correctly aligned.
You should be able to debug/find the problematic code with strace from userspace.
Maybe someone with apparmor knowledge here on the list has an idea?

Helge