Re: CVE-2023-52793: samples/bpf: syscall_tp_user: Fix array out-of-bound access

Re: CVE-2023-52793: samples/bpf: syscall_tp_user: Fix array out-of-bound access

[Shung-Hsi Yu]

On Tue, 21 May 2024 17:31:29 +0200, Greg Kroah-Hartman wrote:
> Description
> ===========
> 
> In the Linux kernel, the following vulnerability has been resolved:
> 
> samples/bpf: syscall_tp_user: Fix array out-of-bound access
> 
> Commit 06744f24696e ("samples/bpf: Add openat2() enter/exit tracepoint
> to syscall_tp sample") added two more eBPF programs to support the
> openat2() syscall. However, it did not increase the size of the array
> that holds the corresponding bpf_links. This leads to an out-of-bound
> access on that array in the bpf_object__for_each_program loop and could
> corrupt other variables on the stack. On our testing QEMU, it corrupts
> the map1_fds array and causes the sample to fail:
> 
>   # ./syscall_tp
>   prog #0: map ids 4 5
>   verify map:4 val: 5
>   map_lookup failed: Bad file descriptor
> 
> Dynamically allocate the array based on the number of programs reported
> by libbpf to prevent similar inconsistencies in the future
> 
> The Linux kernel CVE team has assigned CVE-2023-52793 to this issue.

I would like to dispute this CVE.

Files in samples/bpf are meant to serve as an example and not code that
are directly used at run-time, hence I believe this bug does not have
security implication.

--
Shung-Hsi Yu

> ...

Re: CVE-2023-52793: samples/bpf: syscall_tp_user: Fix array out-of-bound access

[Greg Kroah-Hartman]

On Fri, May 24, 2024 at 11:58:54AM +0800, Shung-Hsi Yu wrote:
> On Tue, 21 May 2024 17:31:29 +0200, Greg Kroah-Hartman wrote:
> > Description
> > ===========
> > 
> > In the Linux kernel, the following vulnerability has been resolved:
> > 
> > samples/bpf: syscall_tp_user: Fix array out-of-bound access
> > 
> > Commit 06744f24696e ("samples/bpf: Add openat2() enter/exit tracepoint
> > to syscall_tp sample") added two more eBPF programs to support the
> > openat2() syscall. However, it did not increase the size of the array
> > that holds the corresponding bpf_links. This leads to an out-of-bound
> > access on that array in the bpf_object__for_each_program loop and could
> > corrupt other variables on the stack. On our testing QEMU, it corrupts
> > the map1_fds array and causes the sample to fail:
> > 
> >   # ./syscall_tp
> >   prog #0: map ids 4 5
> >   verify map:4 val: 5
> >   map_lookup failed: Bad file descriptor
> > 
> > Dynamically allocate the array based on the number of programs reported
> > by libbpf to prevent similar inconsistencies in the future
> > 
> > The Linux kernel CVE team has assigned CVE-2023-52793 to this issue.
> 
> I would like to dispute this CVE.
> 
> Files in samples/bpf are meant to serve as an example and not code that
> are directly used at run-time, hence I believe this bug does not have
> security implication.

You are right, sorry about that, now rejected.  Thanks for the review!

greg k-h