Re: [PATCH v4] acpi: nfit: vmalloc-out-of-bounds Read in acpi_nfit_ctl

[Suraj Sonawane]

On 16/11/24 01:00, Ira Weiny wrote:
> Suraj Sonawane wrote:
> > Fix an issue detected by syzbot with KASAN:
> >
> > BUG: KASAN: vmalloc-out-of-bounds in cmd_to_func drivers/acpi/nfit/
> > core.c:416 [inline]
> > BUG: KASAN: vmalloc-out-of-bounds in acpi_nfit_ctl+0x20e8/0x24a0
> > drivers/acpi/nfit/core.c:459
> >
> > The issue occurs in cmd_to_func when the call_pkg->nd_reserved2
> > array is accessed without verifying that call_pkg points to a buffer
> > that is appropriately sized as a struct nd_cmd_pkg. This can lead
> > to out-of-bounds access and undefined behavior if the buffer does not
> > have sufficient space.
> >
> > To address this, a check was added in acpi_nfit_ctl() to ensure that
> > buf is not NULL and that buf_len is less than sizeof(*call_pkg)
> > before accessing it. This ensures safe access to the members of
> > call_pkg, including the nd_reserved2 array.
> >
> > Reported-by: syzbot+7534f060ebda6b8b51b3@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Closes: https://syzkaller.appspot.com/bug?extid=7534f060ebda6b8b51b3
> > Tested-by: syzbot+7534f060ebda6b8b51b3@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Fixes: ebe9f6f19d80 ("acpi/nfit: Fix bus command validation")
> > Signed-off-by: Suraj Sonawane <surajsonawane0215@xxxxxxxxx>
> > ---
> > V1: https://lore.kernel.org/lkml/20241111080429.9861-1-surajsonawane0215@xxxxxxxxx/
> > V2: Initialized `out_obj` to `NULL` in `acpi_nfit_ctl()` to prevent
> > potential uninitialized variable usage if condition is true.
> > V3: Changed the condition to if (!buf || buf_len < sizeof(*call_pkg))
> > and updated the Fixes tag to reference the correct commit.
> > V4: Removed the explicit cast to maintain the original code style.
> >
> >   drivers/acpi/nfit/core.c | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> > index 5429ec9ef..84d8eef2a 100644
> > --- a/drivers/acpi/nfit/core.c
> > +++ b/drivers/acpi/nfit/core.c
> > @@ -454,8 +454,15 @@ int acpi_nfit_ctl(struct nvdimm_bus_descriptor *nd_desc, struct nvdimm *nvdimm,
> >   	if (cmd_rc)
> >   		*cmd_rc = -EINVAL;
> >   
> > -	if (cmd == ND_CMD_CALL)
> > +	if (cmd == ND_CMD_CALL) {
> > +		if (!buf || buf_len < sizeof(*call_pkg)) {
> > +			rc = -EINVAL;
> > +			goto out;
>
> This goto is wrong.  This will result in ACPI_FREE() being called on an
> undefined out_obj.
>
> This should be:
> 			return -EINVAL;
Thanks for catching that. You’re correct about the goto issue. I had 
initialized out_obj to NULL in previous versions but missed it in this 
patch. In v5, I’ve re-initialized out_obj to NULL, to avoid unintended 
access. Here’s the updated patch link: 
https://lore.kernel.org/lkml/20241116114027.19303-1-surajsonawane0215@xxxxxxxxx/ 


> Ira
>
> > +		}
> > +
> >   		call_pkg = buf;
> > +	}
> > +
> >   	func = cmd_to_func(nfit_mem, cmd, call_pkg, &family);
> >   	if (func < 0)
> >   		return func;
> > --
> > 2.34.1

Best Regards,
Suraj Sonawane