Re: [PATCH] bpf: fix kmalloc bug in bpf_check

On Mon, Sep 13, 2021 at 11:34 PM Yonghong Song [off-list ref] wrote:

On 9/13/21 4:02 AM, Dongliang Mu wrote:

quoted

Since 7661809d493b ("mm: don't allow oversized kvmalloc() calls
") does not allow oversized kvmalloc, it triggers a kmalloc bug warning
at bpf_check.

Fix it by adding a sanity check in th check_btf_line.

Reported-by: syzbot+f3e749d4c662818ae439@syzkaller.appspotmail.com
Fixes: 7661809d493b ("mm: don't allow oversized kvmalloc() calls")
Signed-off-by: Dongliang Mu <redacted>

Thanks for the fix. A similar patch has been proposed here:
https://lore.kernel.org/bpf/20210911005557.45518-1-cuibixuan@huawei.com/ (local)

OK, I see. Let's ignore this patch.

quoted

---
  kernel/bpf/verifier.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 047ac4b4703b..3c5a79f78bc5 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c

@@ -9913,6 +9913,9 @@ static int check_btf_line(struct bpf_verifier_env *env,
      if (!nr_linfo)
              return 0;

+     if (nr_linfo > INT_MAX/sizeof(struct bpf_line_info))
+             return -EINVAL;
+
      rec_size = attr->line_info_rec_size;
      if (rec_size < MIN_BPF_LINEINFO_SIZE ||
          rec_size > MAX_LINEINFO_REC_SIZE ||