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

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Message-ID: <aRxT78fdN5v2Ajyl@p100>
Date: Tue, 18 Nov 2025 12:09:35 +0100
From: Helge Deller <deller@...nel.org>
To: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc: linux-kernel@...r.kernel.org, apparmor@...ts.ubuntu.com,
	John Johansen <john.johansen@...onical.com>,
	linux-security-module@...r.kernel.org, Helge Deller <deller@....de>
Subject: Re: [PATCH 0/2] apparmor unaligned memory fixes

Hi Adrian,

* John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>:
> On Sat, 2025-05-31 at 17:08 +0200, deller@...nel.org wrote:
> > From: Helge Deller <deller@....de>
> > 
> > Two patches which fix unaligned memory accesses in apparmor.
> > Both triggered on the parisc platform, which is much more
> > memory alignment sensitive and will report violations.
> > Please check and apply.
> > 
> > Helge
> > 
> > Helge Deller (2):
> >   apparmor: Fix 8-byte alignment for initial dfa blob streams
> >   apparmor: Fix unaligned memory accesses in KUnit test
> > 
> >  security/apparmor/lsm.c                | 4 ++--
> >  security/apparmor/policy_unpack_test.c | 6 ++++--
> >  2 files changed, 6 insertions(+), 4 deletions(-)
> 
> Thanks for looking into this!
> 
> Unfortunately, the problem still persists on SPARC even with v6.18-rc6:
> 
> [   76.209476] Kernel unaligned access at TPC[8dabfc] aa_dfa_unpack+0x3c/0x6e0
> [   76.301115] Kernel unaligned access at TPC[8dac0c] aa_dfa_unpack+0x4c/0x6e0
> [   76.392697] Kernel unaligned access at TPC[8dacf0] aa_dfa_unpack+0x130/0x6e0
> [   76.485440] Kernel unaligned access at TPC[8dacf0] aa_dfa_unpack+0x130/0x6e0
> [   76.578179] Kernel unaligned access at TPC[8dacf0] aa_dfa_unpack+0x130/0x6e0
> 
> I have documented the problem here [1].
> [1] https://github.com/sparclinux/issues/issues/30
> 
> So, I suspect that your fix is incomplete.

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;