Ah, perfect, I was missing dram_metadata.is_enabled.
And my userland unaligned test case demonstrates that
the second granule is tested, as reported.
** Changed in: qemu
Status: New => Confirmed
** Changed in: qemu
Status: Confirmed => In Progress
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https://bugs.launchpad.net/bugs/1921948
Title:
MTE tags not checked properly for unaligned accesses at EL1
Status in QEMU:
In Progress
Bug description:
For kernel memory accesses that span across two memory granules,
QEMU's MTE implementation only checks the tag of the first granule but
not of the second one.
To reproduce this, build the Linux kernel with CONFIG_KASAN_HW_TAGS
enabled, apply the patch below, and boot the kernel:
diff --git a/sound/last.c b/sound/last.c
index f0bb98780e70..04745cb30b74 100644
--- a/sound/last.c
+++ b/sound/last.c
@@ -5,12 +5,18 @@
*/
#include <linux/init.h>
+#include <linux/slab.h>
#include <sound/core.h>
static int __init alsa_sound_last_init(void)
{
struct snd_card *card;
int idx, ok = 0;
+
+ char *ptr = kmalloc(128, GFP_KERNEL);
+ pr_err("KASAN report should follow:\n");
+ *(volatile unsigned long *)(ptr + 124);
+ kfree(ptr);
printk(KERN_INFO "ALSA device list:\n");
for (idx = 0; idx < SNDRV_CARDS; idx++) {
KASAN tags the 128 allocated bytes with the same tag as the returned
pointer. The memory granule that follows the 128 allocated bytes has a
different tag (with 1/15 probability).
Expected result: a tag fault is detected and a KASAN report is printed when
accessing bytes [124, 130).
Observed result: no tag fault is detected and no KASAN report is printed.
Here are the flags that I use to run QEMU if they matter:
qemu-system-aarch64 -s -machine virt,mte=on -cpu max -m 2G -smp 2 -net
user,host=10.0.2.10,hostfwd=tcp:127.0.0.1:10021-:22 -net nic
-nographic -kernel ./Image -append "console=ttyAMA0 root=/dev/vda
earlyprintk=serial" -drive file=./fs.img,format=raw,if=virtio -no-
shutdown -no-reboot
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