Messages in this thread |  | | Date | Sat, 12 Sep 2020 13:47:06 +0200 | From | Greg KH <> | Subject | Re: [PATCH] Using a pointer and kzalloc in place of a struct directly |
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On Sat, Sep 12, 2020 at 05:08:04PM +0530, Anant Thazhemadam wrote: > Updated the usage of a struct variable directly, in bpf_link_get_info_by_fd > to using a pointer of the same type instead, which points to a memory > location allocated using kzalloc. > > Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
Note, your "To:" line seemed corrupted, and why not cc: the bpf mailing list as well?
Anyway, comment on your patch below:
> diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 4108ef3b828b..01b9c203ef65 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -3605,30 +3605,31 @@ static int bpf_link_get_info_by_fd(struct file *file, > union bpf_attr __user *uattr) > { > struct bpf_link_info __user *uinfo = u64_to_user_ptr(attr->info.info); > - struct bpf_link_info info; > + struct bpf_link_info *info = NULL; > u32 info_len = attr->info.info_len; > int err; > > - err = bpf_check_uarg_tail_zero(uinfo, sizeof(info), info_len); > + err = bpf_check_uarg_tail_zero(uinfo, sizeof(struct bpf_link_info), info_len); > + > if (err) > return err; > info_len = min_t(u32, sizeof(info), info_len); > > - memset(&info, 0, sizeof(info)); > - if (copy_from_user(&info, uinfo, info_len)) > + info = kzalloc(sizeof(struct bpf_link_info), GFP_KERNEL); > + if (copy_from_user(info, uinfo, info_len)) > return -EFAULT;
You leaked memory :(
Did you test this patch? Where do you free this memory, I don't see that happening anywhere in this patch, did I miss it?
And odds are this change will slow things down, right? Why make this change, what's wrong with the structure being on the stack?
thanks,
greg k-h
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