Re: [PATCH v1 0/9] Fixes multiple sysctl bound checks

[Nicolas Bouchinet]

Hi,

Thank's for your reply.

On 1/27/25 19:05, Joe Damato wrote:
> On Mon, Jan 27, 2025 at 03:19:57PM +0100, nicolas.bouchinet@xxxxxxxxxxx wrote:
> > From: Nicolas Bouchinet <nicolas.bouchinet@xxxxxxxxxxx>
> >
> > Hi,
> >
> > This patchset adds some bound checks to sysctls to avoid negative
> > value writes.
> >
> > The patched sysctls were storing the result of the proc_dointvec
> > proc_handler into an unsigned int data. proc_dointvec being able to
> > parse negative value, and it return value being a signed int, this could
> > lead to undefined behaviors.
> > This has led to kernel crash in the past as described in commit
> > 3b3376f222e3 ("sysctl.c: fix underflow value setting risk in vm_table")
> >
> > Most of them are now bounded between SYSCTL_ZERO and SYSCTL_INT_MAX.
> > nf_conntrack_expect_max is bounded between SYSCTL_ONE and SYSCTL_INT_MAX
> > as defined by its documentation.
> I noticed that none of the patches have a Fixes tags. Do any of
> these fix existing crashes or is this just cleanup?

I've just saw that xfrm{4,6}_gc_thresh sysctls where obsolete since 4.14 
in the documentation...

Also, ipv4_dst_ops.gc_thresh is set to `~0` since commit 4ff3885262d0 
("ipv4: Delete routing cache.").

Wich will be printed as -1 when this syctl is read.

```
$ cat /proc/sys/net/ipv4/route/gc_thresh
-1
```

IIUC, it seems to be used in order to disable the garbage collection, 
hence, this patch would make it impossible
to a user to disable it this way.
It should thus be bounded it between SYSCTL_NEG_ONE and SYSCTL_INT_MAX.


Your right, it's only cleanup, I'll push patch 3 separately only on 
netdev, with extended impact analyses, sorry for that.


> I am asking because if this is cleanup then it would be "net-next"
> material instead of "net" and would need to be resubmit when then
> merge window has passed [1].
>
> FWIW, I submit a similar change some time ago and it was submit to
> net-next as cleanup [2].
>
> [1]: https://lore.kernel.org/netdev/20250117182059.7ce1196f@xxxxxxxxxx/
> [2]: https://lore.kernel.org/netdev/CANn89i+=HiffVo9iv2NKMC2LFT15xFLG16h7wN3MCrTiKT3zQQ@xxxxxxxxxxxxxx/T/