* Re: [PATCH v2 00/12] mm/kasan: make kasan=on|off work for all three modes
[not found] <20250812124941.69508-1-bhe@redhat.com>
@ 2025-08-12 13:39 ` Baoquan He
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From: Baoquan He @ 2025-08-12 13:39 UTC (permalink / raw)
To: linux-mm, alexghiti, agordeev, linux, linux-arm-kernel, loongarch,
linuxppc-dev, linux-riscv, christophe.leroy, x86, chris, jcmvbkbc,
linux-um
Cc: ryabinin.a.a, glider, andreyknvl, dvyukov, vincenzo.frascino,
akpm, kasan-dev, linux-kernel, kexec, sj, lorenzo.stoakes, elver,
snovitoll
Forgot adding related ARCH mailing list or people to CC, add them.
On 08/12/25 at 08:49pm, Baoquan He wrote:
> Currently only hw_tags mode of kasan can be enabled or disabled with
> kernel parameter kasan=on|off for built kernel. For kasan generic and
> sw_tags mode, there's no way to disable them once kernel is built.
> This is not convenient sometime, e.g in system kdump is configured.
> When the 1st kernel has KASAN enabled and crash triggered to switch to
> kdump kernel, the generic or sw_tags mode will cost much extra memory
> for kasan shadow while in fact it's meaningless to have kasan in kdump
> kernel.
>
> So this patchset moves the kasan=on|off out of hw_tags scope and into
> common code to make it visible in generic and sw_tags mode too. Then we
> can add kasan=off in kdump kernel to reduce the unneeded meomry cost for
> kasan.
>
> Changelog:
> ====
> v1->v2:
> - Add __ro_after_init for __ro_after_init, and remove redundant blank
> lines in mm/kasan/common.c. Thanks to Marco.
> - Fix a code bug in <linux/kasan-enabled.h> when CONFIG_KASAN is unset,
> this is found out by SeongJae and Lorenzo, and also reported by LKP
> report, thanks to them.
> - Add a missing kasan_enabled() checking in kasan_report(). This will
> cause below KASAN report info even though kasan=off is set:
> ==================================================================
> BUG: KASAN: stack-out-of-bounds in tick_program_event+0x130/0x150
> Read of size 4 at addr ffff00005f747778 by task swapper/0/1
>
> CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.16.0+ #8 PREEMPT(voluntary)
> Hardware name: GIGABYTE R272-P30-JG/MP32-AR0-JG, BIOS F31n (SCP: 2.10.20220810) 09/30/2022
> Call trace:
> show_stack+0x30/0x90 (C)
> dump_stack_lvl+0x7c/0xa0
> print_address_description.constprop.0+0x90/0x310
> print_report+0x104/0x1f0
> kasan_report+0xc8/0x110
> __asan_report_load4_noabort+0x20/0x30
> tick_program_event+0x130/0x150
> ......snip...
> ==================================================================
>
> - Add jump_label_init() calling before kasan_init() in setup_arch() in these
> architectures: xtensa, arm. Because they currenly rely on
> jump_label_init() in main() which is a little late. Then the early static
> key kasan_flag_enabled in kasan_init() won't work.
>
> - In UML architecture, change to enable kasan_flag_enabled in arch_mm_preinit()
> because kasan_init() is enabled before main(), there's no chance to operate
> on static key in kasan_init().
>
> Test:
> =====
> In v1, I took test on x86_64 for generic mode, and on arm64 for
> generic, sw_tags and hw_tags mode. All of them works well.
>
> In v2, I only tested on arm64 for generic, sw_tags and hw_tags mode, it
> works. For powerpc, I got a BOOK3S/64 machine, while it says
> 'KASAN not enabled as it requires radix' and KASAN is disabled. Will
> look for other POWER machine to test this.
> ====
>
> Baoquan He (12):
> mm/kasan: add conditional checks in functions to return directly if
> kasan is disabled
> mm/kasan: move kasan= code to common place
> mm/kasan/sw_tags: don't initialize kasan if it's disabled
> arch/arm: don't initialize kasan if it's disabled
> arch/arm64: don't initialize kasan if it's disabled
> arch/loongarch: don't initialize kasan if it's disabled
> arch/powerpc: don't initialize kasan if it's disabled
> arch/riscv: don't initialize kasan if it's disabled
> arch/x86: don't initialize kasan if it's disabled
> arch/xtensa: don't initialize kasan if it's disabled
> arch/um: don't initialize kasan if it's disabled
> mm/kasan: make kasan=on|off take effect for all three modes
>
> arch/arm/kernel/setup.c | 6 +++++
> arch/arm/mm/kasan_init.c | 6 +++++
> arch/arm64/mm/kasan_init.c | 7 ++++++
> arch/loongarch/mm/kasan_init.c | 5 ++++
> arch/powerpc/mm/kasan/init_32.c | 8 +++++-
> arch/powerpc/mm/kasan/init_book3e_64.c | 6 +++++
> arch/powerpc/mm/kasan/init_book3s_64.c | 6 +++++
> arch/riscv/mm/kasan_init.c | 6 +++++
> arch/um/kernel/mem.c | 6 +++++
> arch/x86/mm/kasan_init_64.c | 6 +++++
> arch/xtensa/kernel/setup.c | 1 +
> arch/xtensa/mm/kasan_init.c | 6 +++++
> include/linux/kasan-enabled.h | 18 ++++++-------
> mm/kasan/common.c | 25 ++++++++++++++++++
> mm/kasan/generic.c | 20 +++++++++++++--
> mm/kasan/hw_tags.c | 35 ++------------------------
> mm/kasan/init.c | 6 +++++
> mm/kasan/quarantine.c | 3 +++
> mm/kasan/report.c | 4 ++-
> mm/kasan/shadow.c | 23 ++++++++++++++++-
> mm/kasan/sw_tags.c | 9 +++++++
> 21 files changed, 165 insertions(+), 47 deletions(-)
>
> --
> 2.41.0
>
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