* (no subject)
@ 2025-08-12 13:34 Baoquan He
2025-08-12 13:49 ` Baoquan He
0 siblings, 1 reply; 2+ messages in thread
From: Baoquan He @ 2025-08-12 13:34 UTC (permalink / raw)
To: linux-mm, christophe.leroy
alexghiti@rivosinc.com, agordeev@linux.ibm.com, linux@armlinux.org.uk,
linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev,
linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
x86@kernel.org, chris@zankel.net, jcmvbkbc@gmail.com, linux-um@lists.infradead.org
Cc: ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com,
dvyukov@google.com, vincenzo.frascino@arm.com,
akpm@linux-foundation.org, kasan-dev@googlegroups.com,
linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
sj@kernel.org, lorenzo.stoakes@oracle.com, elver@google.com,
snovitoll@gmail.com
Bcc: bhe@redhat.com
Subject: Re: [PATCH v2 00/12] mm/kasan: make kasan=on|off work for all three
modes
Reply-To:
In-Reply-To: <20250812124941.69508-1-bhe@redhat.com>
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
>
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re:
2025-08-12 13:34 Baoquan He
@ 2025-08-12 13:49 ` Baoquan He
0 siblings, 0 replies; 2+ messages in thread
From: Baoquan He @ 2025-08-12 13:49 UTC (permalink / raw)
To: linux-mm, christophe.leroy
On 08/12/25 at 09:34pm, Baoquan He wrote:
> alexghiti@rivosinc.com, agordeev@linux.ibm.com, linux@armlinux.org.uk,
> linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev,
> linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
> x86@kernel.org, chris@zankel.net, jcmvbkbc@gmail.com, linux-um@lists.infradead.org
> Cc: ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com,
> dvyukov@google.com, vincenzo.frascino@arm.com,
> akpm@linux-foundation.org, kasan-dev@googlegroups.com,
> linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
> sj@kernel.org, lorenzo.stoakes@oracle.com, elver@google.com,
> snovitoll@gmail.com
> Bcc: bhe@redhat.com
> Subject: Re: [PATCH v2 00/12] mm/kasan: make kasan=on|off work for all three
> modes
> Reply-To:
> In-Reply-To: <20250812124941.69508-1-bhe@redhat.com>
>
> Forgot adding related ARCH mailing list or people to CC, add them.
Sorry for the noise, I made mistake on mail format when adding people to
CC.
>
> 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
> >
>
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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