[PATCH 6.6.y 1/2] AppArmor: Allow apparmor to handle unaligned dfa tables

[Artem Dinaburg <artem@trailofbits.com>]

From: Helge Deller <deller@kernel.org>

[ Upstream commit 64802f731214a51dfe3c6c27636b3ddafd003eb0 ]

The dfa tables can originate from kernel or userspace and 8-byte alignment
isn't always guaranteed and as such may trigger unaligned memory accesses
on various architectures. Resulting in the following

[   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

Work around it by using the get_unaligned_xx() helpers.

[ Backport to 6.6.y: Use asm/unaligned.h because the target predates
  linux/unaligned.h, keeping this first patch independently buildable. ]

Fixes: e6e8bf418850d ("apparmor: fix restricted endian type warnings for dfa unpack")
Reported-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Closes: https://github.com/sparclinux/issues/issues/30
Signed-off-by: Helge Deller <deller@gmx.de>
Signed-off-by: John Johansen <john.johansen@canonical.com>
Assisted-by: LLM
Signed-off-by: Artem Dinaburg <artem@trailofbits.com>
---
This is patch 1 of 2 in the ordered 6.6.y backport series.
This change addresses CVE-2026-46254. Both DFA unpackers cast blob offsets
to aligned big-endian pointers even though policy blobs need not be
aligned.
This needed a target-specific adjustment; I called it out in the bracketed
backport note above.

The fix is already present in 6.12.y, 6.18.y, and 7.2.y, but not in 6.6.y.
This fix also affects 6.1.y, which will need a separate backport; this
submission contains only the 6.6.y patch.

 security/apparmor/match.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/security/apparmor/match.c b/security/apparmor/match.c
index 29e728f6fbcf..19b44e705b26 100644
--- a/security/apparmor/match.c
+++ b/security/apparmor/match.c
@@ -15,6 +15,7 @@
 #include <linux/vmalloc.h>
 #include <linux/err.h>
 #include <linux/kref.h>
+#include <asm/unaligned.h>
 
 #include "include/lib.h"
 #include "include/match.h"
@@ -42,11 +43,11 @@ static struct table_header *unpack_table(char *blob, size_t bsize)
 	/* loaded td_id's start at 1, subtract 1 now to avoid doing
 	 * it every time we use td_id as an index
 	 */
-	th.td_id = be16_to_cpu(*(__be16 *) (blob)) - 1;
+	th.td_id = get_unaligned_be16(blob) - 1;
 	if (th.td_id > YYTD_ID_MAX)
 		goto out;
-	th.td_flags = be16_to_cpu(*(__be16 *) (blob + 2));
-	th.td_lolen = be32_to_cpu(*(__be32 *) (blob + 8));
+	th.td_flags = get_unaligned_be16(blob + 2);
+	th.td_lolen = get_unaligned_be32(blob + 8);
 	blob += sizeof(struct table_header);
 
 	if (!(th.td_flags == YYTD_DATA16 || th.td_flags == YYTD_DATA32 ||
@@ -293,14 +294,14 @@ struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
 	if (size < sizeof(struct table_set_header))
 		goto fail;
 
-	if (ntohl(*(__be32 *) data) != YYTH_MAGIC)
+	if (get_unaligned_be32(data) != YYTH_MAGIC)
 		goto fail;
 
-	hsize = ntohl(*(__be32 *) (data + 4));
+	hsize = get_unaligned_be32(data + 4);
 	if (size < hsize)
 		goto fail;
 
-	dfa->flags = ntohs(*(__be16 *) (data + 12));
+	dfa->flags = get_unaligned_be16(data + 12);
 	if (dfa->flags & ~(YYTH_FLAGS))
 		goto fail;
 
@@ -309,7 +310,7 @@ struct aa_dfa *aa_dfa_unpack(void *blob, size_t size, int flags)
 	 * if (dfa->flags & YYTH_FLAGS_OOB_TRANS) {
 	 *	if (hsize < 16 + 4)
 	 *		goto fail;
-	 *	dfa->max_oob = ntol(*(__be32 *) (data + 16));
+	 *	dfa->max_oob = get_unaligned_be32(data + 16);
 	 *	if (dfa->max <= MAX_OOB_SUPPORTED) {
 	 *		pr_err("AppArmor DFA OOB greater than supported\n");
 	 *		goto fail;
-- 
2.39.5