Re: [RESEND PATCH] cxl/features: Ensure that count is set before access to end[] __counted_by()

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 11 Sep 2026 14:58:29 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

Typo in patch title end/ent[]

(might be mine given I suggested a title to Ashok during internal review!)

Hopefully Dave won't mind fixing that whilst picking it up.

> On 9/11/26 2:53 PM, Ashok Raj wrote:
> > get_supported_features() assigns entries->num_features only after the
> > memcpy() loop that fills entries->ent[] has already run. Since ent[]
> > is __counted_by(num_features), the compiler's bounds instrumentation
> > sees a 0-length array during that loop and FORTIFY_SOURCE trips on
> > the memcpy. Set @num_features right after allocation, before any
> > write into ent[], so the bound is correct for the whole lifetime of
> > the array.
> > 
> > This was found via a fortify panic:
> > 
> >  memcpy: detected buffer overflow: 384 byte write of buffer size 0
> >  WARNING: lib/string_helpers.c:1035 at __fortify_report+0x54/0xa0
> >  kernel BUG at lib/string_helpers.c:1043!
> >  Call trace:
> >   __fortify_panic+0x10/0x18
> >   get_supported_features.isra.0+0x4a0/0x4d0 [cxl_core]
> >   devm_cxl_setup_features+0x84/0x120 [cxl_core]
> >   cxl_pci_probe+0x254/0x5e0 [cxl_pci]
> > 
> > Same class of bug, same fix shape as commit 6c9d2e87df40
> > ("cxl/fwctl: Fix __fortify_panic"), which fixed the analogous issue
> > in cxlctl_get_supported_features() but missed this one.
> > 
> > Fixes: f0e6a2329bf9 ("cxl: Add Get Supported Features command for kernel usage")
> > Signed-off-by: Ashok Raj <ashok.raj@oss.qualcomm.com>  
> 
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>

Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>