Hi Hou,
On Fri, Sep 08, 2023 at 09:39:22PM +0800, Hou Tao wrote:
> From: Hou Tao <houtao1@xxxxxxxxxx>
>
> Add extra check in bpf_mem_alloc_init() to ensure the unit_size of
> bpf_mem_cache is matched with the object_size of underlying slab cache.
> If these two sizes are unmatched, print a warning once and return
> -EINVAL in bpf_mem_alloc_init(), so the mismatch can be found early and
> the potential issue can be prevented.
>
> Suggested-by: Alexei Starovoitov <ast@xxxxxxxxxx>
> Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
> ---
> kernel/bpf/memalloc.c | 33 +++++++++++++++++++++++++++++++--
> 1 file changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/memalloc.c b/kernel/bpf/memalloc.c
> index 90c1ed8210a2..1c22b90e754a 100644
> --- a/kernel/bpf/memalloc.c
> +++ b/kernel/bpf/memalloc.c
> @@ -486,6 +486,24 @@ static void prefill_mem_cache(struct bpf_mem_cache *c, int cpu)
> alloc_bulk(c, c->unit_size <= 256 ? 4 : 1, cpu_to_node(cpu), false);
> }
>
> +static int check_obj_size(struct bpf_mem_cache *c, unsigned int idx)
> +{
> + struct llist_node *first;
> + unsigned int obj_size;
> +
> + first = c->free_llist.first;
> + if (!first)
> + return 0;
> +
> + obj_size = ksize(first);
> + if (obj_size != c->unit_size) {
> + WARN_ONCE(1, "bpf_mem_cache[%u]: unexpected object size %u, expect %u\n",
> + idx, obj_size, c->unit_size);
> + return -EINVAL;
> + }
> + return 0;
> +}
I am seeing the warning added by this change as commit c93047255202
("bpf: Ensure unit_size is matched with slab cache object size") when
booting ARCH=riscv defconfig in QEMU. I have seen some discussion on the
mailing list around this, so I apologize if this is a duplicate report
but it sounded like the previously reported instance of this warning was
already resolved by some other changeor supposed to be resolved by [1].
Unfortunately, I tested both current bpf master (currently at
6bd5bcb18f94) with and without that change and I still see the warning
in both cases. The rootfs is available at [2], if it is relevant.
$ make -skj"$(nproc)" ARCH=riscv CROSS_COMPILE=riscv64-linux- mrproper defconfig Image
$ qemu-system-riscv64 \
-display none \
-nodefaults \
-bios default \
-M virt \
-append earlycon \
-kernel arch/riscv/boot/Image \
-initrd riscv-rootfs.cpio \
-m 512m \
-serial mon:stdio
...
[ 0.000000] Linux version 6.5.0-12679-gc93047255202 (nathan@dev-arch.thelio-3990X) (riscv64-linux-gcc (GCC) 13.2.0, GNU ld (GNU Binutils) 2.41) #1 SMP Thu Sep 14 10:44:41 MST 2023
...
[ 0.433002] ------------[ cut here ]------------
[ 0.433128] bpf_mem_cache[0]: unexpected object size 128, expect 96
[ 0.433585] WARNING: CPU: 0 PID: 1 at kernel/bpf/memalloc.c:500 bpf_mem_alloc_init+0x348/0x354
[ 0.433810] Modules linked in:
[ 0.433928] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.5.0-12679-gc93047255202 #1
[ 0.434025] Hardware name: riscv-virtio,qemu (DT)
[ 0.434105] epc : bpf_mem_alloc_init+0x348/0x354
[ 0.434140] ra : bpf_mem_alloc_init+0x348/0x354
[ 0.434163] epc : ffffffff80112572 ra : ffffffff80112572 sp : ff2000000000bd30
[ 0.434177] gp : ffffffff81501588 tp : ff600000018d0000 t0 : ffffffff808cd1a0
[ 0.434190] t1 : 0720072007200720 t2 : 635f6d656d5f6670 s0 : ff2000000000bdd0
[ 0.434202] s1 : ffffffff80e17620 a0 : 0000000000000037 a1 : ffffffff814866b8
[ 0.434215] a2 : 0000000000000000 a3 : 0000000000000001 a4 : 0000000000000000
[ 0.434227] a5 : 0000000000000000 a6 : 0000000000000047 a7 : 0000000000000046
[ 0.434239] s2 : 000000000000000b s3 : 0000000000000000 s4 : 0000000000000000
[ 0.434251] s5 : 0000000000000100 s6 : ffffffff815031f8 s7 : ffffffff8153a610
[ 0.434264] s8 : 0000000000000060 s9 : 0000000000000060 s10: 0000000000000000
[ 0.434276] s11: ff6000001ffe5410 t3 : ff60000001858f00 t4 : ff60000001858f00
[ 0.434288] t5 : ff60000001858000 t6 : ff2000000000bb48
[ 0.434299] status: 0000000200000120 badaddr: 0000000000000000 cause: 0000000000000003
[ 0.434394] [<ffffffff80112572>] bpf_mem_alloc_init+0x348/0x354
[ 0.434492] [<ffffffff80a0f302>] bpf_global_ma_init+0x1c/0x30
[ 0.434516] [<ffffffff8000212c>] do_one_initcall+0x58/0x19c
[ 0.434526] [<ffffffff80a0105e>] kernel_init_freeable+0x214/0x27e
[ 0.434537] [<ffffffff808db4dc>] kernel_init+0x1e/0x10a
[ 0.434548] [<ffffffff80003386>] ret_from_fork+0xa/0x1c
[ 0.434618] ---[ end trace 0000000000000000 ]---
[1]: https://lore.kernel.org/20230913135943.3137292-1-houtao@xxxxxxxxxxxxxxx/
[2]: https://github.com/ClangBuiltLinux/boot-utils/releases
Cheers,
Nathan
# bad: [98897dc735cf6635f0966f76eb0108354168fb15] Add linux-next specific files for 20230914
# good: [aed8aee11130a954356200afa3f1b8753e8a9482] Merge tag 'pmdomain-v6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/linux-pm
git bisect start '98897dc735cf6635f0966f76eb0108354168fb15' 'aed8aee11130a954356200afa3f1b8753e8a9482'
# good: [ea1bbd78a48c8b325583e8c0bc2690850cb51807] bcachefs: Fix assorted checkpatch nits
git bisect good ea1bbd78a48c8b325583e8c0bc2690850cb51807
# bad: [9c4e2139cfa15d769eafd51bf3e051293b106986] Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next.git
git bisect bad 9c4e2139cfa15d769eafd51bf3e051293b106986
# bad: [4f07b13481ab390108b015da2bc8f560416e48d2] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/qcom/linux.git
git bisect bad 4f07b13481ab390108b015da2bc8f560416e48d2
# bad: [bcfe98207530e1ea0004f4e5dbd6e7e4d9eb2471] Merge branch 'for-linux-next-fixes' of git://anongit.freedesktop.org/drm/drm-misc
git bisect bad bcfe98207530e1ea0004f4e5dbd6e7e4d9eb2471
# bad: [95d3e99b1ca8ad3da86c525cc1c00e4ba27592ac] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wireless/wireless.git
git bisect bad 95d3e99b1ca8ad3da86c525cc1c00e4ba27592ac
# good: [6836d373943afeeeb8e2989c22aaaa51218a83c6] Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc.git
git bisect good 6836d373943afeeeb8e2989c22aaaa51218a83c6
# good: [3d3e2fb5e45a08a45ae01f0dfaf9621ae0e439f9] Merge branch 'main' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git
git bisect good 3d3e2fb5e45a08a45ae01f0dfaf9621ae0e439f9
# bad: [51d56d51d3881addaea2c7242ae859155ae75607] Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec.git
git bisect bad 51d56d51d3881addaea2c7242ae859155ae75607
# bad: [1a49f4195d3498fe458a7f5ff7ec5385da70d92e] bpf: Avoid dummy bpf_offload_netdev in __bpf_prog_dev_bound_init
git bisect bad 1a49f4195d3498fe458a7f5ff7ec5385da70d92e
# bad: [c930472552022bd09aab3cd946ba3f243070d5c7] bpf: Ensure unit_size is matched with slab cache object size
git bisect bad c930472552022bd09aab3cd946ba3f243070d5c7
# good: [7182e56411b9a8b76797ed7b6095fc84be76dfb0] selftests/bpf: Add kprobe_multi override test
git bisect good 7182e56411b9a8b76797ed7b6095fc84be76dfb0
# good: [b1d53958b69312e43c118d4093d8f93d3f6f80af] bpf: Don't prefill for unused bpf_mem_cache
git bisect good b1d53958b69312e43c118d4093d8f93d3f6f80af
# first bad commit: [c930472552022bd09aab3cd946ba3f243070d5c7] bpf: Ensure unit_size is matched with slab cache object size
