Fedora Account System
Red Hat Associate
Red Hat Customer
1. Please describe the problem: There is a new kernel option in town, `CONFIG_KASAN_HW_TAGS`, making use of aarch64's MTE/TBI to power KASAN. The performance impact is super-duper-low, and it'll likely uncover memory corruption issues. The main drawback is that, well, it'll find memory corruption issues, but this can be mitigated by using `kasan.fault=report`, so that the issues will be reported and the kernel won't be panic'ed. Another mitigating factor is that statistically ~nobody is running fedora on aarch64, except via the asahi linux remix, so the number of affected users should be low-ish. It's currently enabled by default on android: https://source.android.com/docs/security/test/memory-safety/arm-mte#mte-in-kernel 2. What is the Version-Release number of the kernel: N/A 3. Did it work previously in Fedora? If so, what kernel version did the issue *first* appear? Old kernels are available for download at https://koji.fedoraproject.org/koji/packageinfo?packageID=8 : No 4. Can you reproduce this issue? If so, please provide the steps to reproduce the issue below: Compile the kernel with the proper option, notice that it doesn't break anything, doesn't tank the performances, and results in some "memory corruption in kernel-land, oh no :<" message from time to time. 5. Does this problem occur with the latest Rawhide kernel? To install the Rawhide kernel, run ``sudo dnf install fedora-repos-rawhide`` followed by ``sudo dnf update --enablerepo=rawhide kernel``: N/A 6. Are you running any modules that not shipped with directly Fedora's kernel?: N/A 7. Please attach the kernel logs. You can get the complete kernel log for a boot with ``journalctl --no-hostname -k > dmesg.txt``. If the issue occurred on a previous boot, use the journalctl ``-b`` flag. N/A Reproducible: Always
While KASAN is only enabled for debug kernels, I have turned this on in rawhide and it will roll out as 6.10 rebases are done.
The [documentation]( https://www.kernel.org/doc/html/latest/dev-tools/kasan.html ) states: > Hardware Tag-Based KASAN or HW_TAGS KASAN, enabled with CONFIG_KASAN_HW_TAGS, is the mode intended to be used as an in-field memory bug detector or as a security mitigation. This mode only works on arm64 CPUs that support MTE (Memory Tagging Extension), but it has low memory and performance overheads and thus can be used in production. Would it be possible to enable it for the prod kernel as well on aarch64?
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Still an issue now, marked as such.