Re: Stable backport request: skbuff: Proactively round up to kmalloc bucket size

["Daniel Díaz" <daniel.diaz@linaro.org>]

Hello!

On Mon, 22 May 2023 at 12:37, Nick Desaulniers <ndesaulniers@google.com> wrote:
>
> On Mon, May 22, 2023 at 11:24 AM Daniel Díaz <daniel.diaz@linaro.org> wrote:
> >
> > Hello!
> >
> > Would the stable maintainers please consider backporting the following
> > commit to the 6.1? We are trying to build gki_defconfig (plus a few
>
> Does android's gki_defconfig fail to boot on the `android14-6.1`
> branch of https://android.googlesource.com/kernel/common?
>
> (i.e. downstream branch from linux stable's linux-6.1.y)?
>
> We just ran CI successfully on that branch 10 hours ago.
> https://github.com/ClangBuiltLinux/continuous-integration2/actions/runs/5042504560/jobs/9045030265
>
> Do you have more information on the observed boot failure? (panic splat?)

Apologies if it sounded like we were trying to boot an Android kernel.
Let me clarify: We're booting v6.1.29 from linux-stable/linux-6.1.y.

This is what we get under Qemu-arm64 for v6.1.29 with Clang 16:
-----8<-----
  Unexpected kernel BRK exception at EL1
  Internal error: BRK handler: 00000000f2000001 [#1] PREEMPT SMP
  Modules linked in:
  CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.1.29 #1
  Hardware name: linux,dummy-virt (DT)
  pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  pc : pskb_expand_head+0x448/0x480
  lr : pskb_expand_head+0x13c/0x480
  sp : ffff80000802b850
  x29: ffff80000802b860 x28: 00000000000002c0 x27: 0000000000000ec0
  x26: ffff0000c02c8ec0 x25: ffff0000c02c8000 x24: 00000000000128c0
  x23: ffff0000c030e800 x22: ffff0000c030e800 x21: 0000000000000240
  x20: 0000000000000000 x19: ffff0000c085e900 x18: ffff800008021068
  x17: 00000000ad6b63b6 x16: 00000000ad6b63b6 x15: 0001001c00070038
  x14: 0000000c00020008 x13: 00882cc00000ffff x12: 0000000000000000
  x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000001
  x8 : ffff0000c030eac0 x7 : 0000000000000000 x6 : 0000000000000000
  x5 : ffff0000c030eaf0 x4 : ffff0000ff7abd10 x3 : 0000000000001740
  x2 : ffff0000c02c8000 x1 : 0000000000000000 x0 : 0000000000000000
  Call trace:
   pskb_expand_head+0x448/0x480
   netlink_trim+0xa0/0xc8
   netlink_broadcast+0x54/0x764
   genl_ctrl_event+0x21c/0x37c
   genl_register_family+0x628/0x708
   thermal_netlink_init+0x28/0x3c
   thermal_init+0x28/0xec
   do_one_initcall+0xfc/0x358
   do_initcall_level+0xd8/0x1b4
   do_initcalls+0x64/0xa8
   do_basic_setup+0x2c/0x3c
   kernel_init_freeable+0x118/0x198
   kernel_init+0x30/0x1c0
   ret_from_fork+0x10/0x20
  Code: f9406679 38776b28 3707eba8 17ffff67 (d4200020)
  ---[ end trace 0000000000000000 ]---
  Kernel panic - not syncing: BRK handler: Fatal exception
  SMP: stopping secondary CPUs
----->8-----

Here's a link to that test, with all artifacts:
https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/daniel/tests/2QA2CVTTvG6KZETMUyZCNgS8koR

This can be reproduced locally via Tuxrun:
-----8<-----
#pip3 install -U tuxrun
tuxrun --runtime podman \
  --device qemu-arm64 \
  --image docker.io/lavasoftware/lava-dispatcher:2023.01.0020.gc1598238f \
  --boot-args rw \
  --kernel https://storage.tuxsuite.com/public/linaro/daniel/builds/2QA2CHQUpqKe27FyMZrBNILVwXi/Image.gz
\
  --modules https://storage.tuxsuite.com/public/linaro/daniel/builds/2QA2CHQUpqKe27FyMZrBNILVwXi/modules.tar.xz
\
  --rootfs https://storage.tuxboot.com/debian/bookworm/arm64/rootfs.ext4.xz
----->8-----

This is vanilla v6.1.29 with no extra patches, just this kernel configuration:
  https://storage.tuxsuite.com/public/linaro/daniel/builds/2QA2CHQUpqKe27FyMZrBNILVwXi/config

Greetings!

Daniel Díaz
daniel.diaz@linaro.org



> > extras) on Arm64 and test it under Qemu-arm64, but it fails to boot.
> > Bisection has pointed here.
> >
> > We have verified that cherry-picking this patch on top of v6.1.29
> > applies cleanly and allows the kernel to boot.
> >
> > commit 12d6c1d3a2ad0c199ec57c201cdc71e8e157a232
> > Author: Kees Cook <keescook@chromium.org>
> > Date:   Tue Oct 25 15:39:35 2022 -0700
> >
> >     skbuff: Proactively round up to kmalloc bucket size
> >
> >     Instead of discovering the kmalloc bucket size _after_ allocation, round
> >     up proactively so the allocation is explicitly made for the full size,
> >     allowing the compiler to correctly reason about the resulting size of
> >     the buffer through the existing __alloc_size() hint.
> >
> >     This will allow for kernels built with CONFIG_UBSAN_BOUNDS or the
> >     coming dynamic bounds checking under CONFIG_FORTIFY_SOURCE to gain
> >     back the __alloc_size() hints that were temporarily reverted in commit
> >     93dd04ab0b2b ("slab: remove __alloc_size attribute from
> > __kmalloc_track_caller")
> >
> >     Cc: "David S. Miller" <davem@davemloft.net>
> >     Cc: Eric Dumazet <edumazet@google.com>
> >     Cc: Jakub Kicinski <kuba@kernel.org>
> >     Cc: Paolo Abeni <pabeni@redhat.com>
> >     Cc: netdev@vger.kernel.org
> >     Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >     Cc: Nick Desaulniers <ndesaulniers@google.com>
> >     Cc: David Rientjes <rientjes@google.com>
> >     Acked-by: Vlastimil Babka <vbabka@suse.cz>
> >     Link: https://patchwork.kernel.org/project/netdevbpf/patch/20221021234713.you.031-kees@kernel.org/
> >     Signed-off-by: Kees Cook <keescook@chromium.org>
> >     Link: https://lore.kernel.org/r/20221025223811.up.360-kees@kernel.org
> >     Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> >
> >
> > Thanks and greetings!
> >
> > Daniel Díaz
> > daniel.diaz@linaro.org
>
>
>
> --
> Thanks,
> ~Nick Desaulniers