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Message-ID: <CAG_fn=UbWvN=FiXjU_QZKm_qDhxU8dZQ4fgELXsRsPCj4YHp9A@mail.gmail.com> Date: Tue, 3 Sep 2024 17:39:28 +0200 From: Alexander Potapenko <glider@...gle.com> To: samuel.holland@...ive.com, Andrey Konovalov <andreyknvl@...il.com> Cc: Marc Zyngier <maz@...nel.org>, Aleksandr Nogikh <nogikh@...gle.com>, kasan-dev <kasan-dev@...glegroups.com>, Will Deacon <will@...nel.org>, syzbot <syzbot+908886656a02769af987@...kaller.appspotmail.com>, catalin.marinas@....com, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com Subject: Re: [syzbot] [arm?] upstream test error: KASAN: invalid-access Write in setup_arch On Mon, Sep 2, 2024 at 12:03 PM 'Aleksandr Nogikh' via kasan-dev <kasan-dev@...glegroups.com> wrote: > > +kasan-dev > > On Sat, Aug 31, 2024 at 7:53 PM 'Marc Zyngier' via syzkaller-bugs > <syzkaller-bugs@...glegroups.com> wrote: > > > > On Fri, 30 Aug 2024 10:52:54 +0100, > > Will Deacon <will@...nel.org> wrote: > > > > > > On Fri, Aug 30, 2024 at 01:35:24AM -0700, syzbot wrote: > > > > Hello, > > > > > > > > syzbot found the following issue on: > > > > > > > > HEAD commit: 33faa93bc856 Merge branch kvmarm-master/next into kvmarm-m.. > > > > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git fuzzme > > > > > > +Marc, as this is his branch. > > > > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=1398420b980000 > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=2b7b31c9aa1397ca > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=908886656a02769af987 > > > > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > > > > userspace arch: arm64 > > > > As it turns out, this isn't specific to this branch. I can reproduce > > it with this config on a vanilla 6.10 as a KVM guest. Even worse, > > compiling with clang results in an unbootable kernel (without any > > output at all). > > > > Mind you, the binary is absolutely massive (130MB with gcc, 156MB with > > clang), and I wouldn't be surprised if we were hitting some kind of > > odd limit. > > > > > > > > > > Downloadable assets: > > > > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/384ffdcca292/non_bootable_disk-33faa93b.raw.xz > > > > vmlinux: https://storage.googleapis.com/syzbot-assets/9093742fcee9/vmlinux-33faa93b.xz > > > > kernel image: https://storage.googleapis.com/syzbot-assets/b1f599907931/Image-33faa93b.gz.xz > > > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > > Reported-by: syzbot+908886656a02769af987@...kaller.appspotmail.com > > > > > > > > Booting Linux on physical CPU 0x0000000000 [0x000f0510] > > > > Linux version 6.11.0-rc5-syzkaller-g33faa93bc856 (syzkaller@...kaller) (gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40) #0 SMP PREEMPT now > > > > random: crng init done > > > > Machine model: linux,dummy-virt > > > > efi: UEFI not found. > > > > NUMA: No NUMA configuration found > > > > NUMA: Faking a node at [mem 0x0000000040000000-0x00000000bfffffff] > > > > NUMA: NODE_DATA [mem 0xbfc1d340-0xbfc20fff] > > > > Zone ranges: > > > > DMA [mem 0x0000000040000000-0x00000000bfffffff] > > > > DMA32 empty > > > > Normal empty > > > > Device empty > > > > Movable zone start for each node > > > > Early memory node ranges > > > > node 0: [mem 0x0000000040000000-0x00000000bfffffff] > > > > Initmem setup node 0 [mem 0x0000000040000000-0x00000000bfffffff] > > > > cma: Reserved 32 MiB at 0x00000000bba00000 on node -1 > > > > psci: probing for conduit method from DT. > > > > psci: PSCIv1.1 detected in firmware. > > > > psci: Using standard PSCI v0.2 function IDs > > > > psci: Trusted OS migration not required > > > > psci: SMC Calling Convention v1.0 > > > > ================================================================== > > > > BUG: KASAN: invalid-access in smp_build_mpidr_hash arch/arm64/kernel/setup.c:133 [inline] > > > > BUG: KASAN: invalid-access in setup_arch+0x984/0xd60 arch/arm64/kernel/setup.c:356 > > > > Write of size 4 at addr 03ff800086867e00 by task swapper/0 > > > > Pointer tag: [03], memory tag: [fe] > > > > > > > > CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.11.0-rc5-syzkaller-g33faa93bc856 #0 > > > > Hardware name: linux,dummy-virt (DT) > > > > Call trace: > > > > dump_backtrace+0x204/0x3b8 arch/arm64/kernel/stacktrace.c:317 > > > > show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:324 > > > > __dump_stack lib/dump_stack.c:93 [inline] > > > > dump_stack_lvl+0x260/0x3b4 lib/dump_stack.c:119 > > > > print_address_description mm/kasan/report.c:377 [inline] > > > > print_report+0x118/0x5ac mm/kasan/report.c:488 > > > > kasan_report+0xc8/0x108 mm/kasan/report.c:601 > > > > kasan_check_range+0x94/0xb8 mm/kasan/sw_tags.c:84 > > > > __hwasan_store4_noabort+0x20/0x2c mm/kasan/sw_tags.c:149 > > > > smp_build_mpidr_hash arch/arm64/kernel/setup.c:133 [inline] > > > > setup_arch+0x984/0xd60 arch/arm64/kernel/setup.c:356 > > > > start_kernel+0xe0/0xff0 init/main.c:926 > > > > __primary_switched+0x84/0x8c arch/arm64/kernel/head.S:243 > > > > > > > > The buggy address belongs to stack of task swapper/0 > > > > > > > > Memory state around the buggy address: > > > > ffff800086867c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > > > > ffff800086867d00: 00 fe fe 00 00 00 fe fe fe fe fe fe fe fe fe fe > > > > >ffff800086867e00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe > > > > ^ > > > > ffff800086867f00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe > > > > ffff800086868000: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe > > > > ================================================================== > > > > > > I can't spot the issue here. We have a couple of fixed-length > > > (4 element) arrays on the stack and they're indexed by a simple loop > > > counter that runs from 0-3. > > > > Having trimmed the config to the extreme, I can only trigger the > > warning with CONFIG_KASAN_SW_TAGS (CONFIG_KASAN_GENERIC does not > > scream). Same thing if I use gcc 14.2.0. > > > > However, compiling with clang 14 (Debian clang version 14.0.6) does > > *not* result in a screaming kernel, even with KASAN_SW_TAGS. > > > > So I can see two possibilities here: > > > > - either gcc is incompatible with KASAN_SW_TAGS and the generic > > version is the only one that works > > > > - or we have a compiler bug on our hands. > > > > Frankly, I can't believe the later, as the code is so daft that I > > can't imagine gcc getting it *that* wrong. > > > > Who knows enough about KASAN to dig into this? This looks related to Samuel's "arm64: Fix KASAN random tag seed initialization" patch that landed in August. I am a bit surprised the bug is reported before the "KernelAddressSanitizer initialized" banner is printed - I thought we shouldn't be reporting anything until the tool is fully initialized.
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