RE: [PATCH 5.10.y] e1000e: fix EEPROM length types for overflow checks

["Farber, Eliav" <farbere@amazon.com>]

> On Thu, Sep 11, 2025 at 06:13:33AM +0000, Farber, Eliav wrote:
> > > On Wed, Sep 10, 2025 at 05:31:38PM +0000, Eliav Farber wrote:
> > >> Fix a compilation failure when warnings are treated as errors:
> > >>
> > >> drivers/net/ethernet/intel/e1000e/ethtool.c: In function ‘e1000_set_eeprom’:
> > >> ./include/linux/overflow.h:71:15: error: comparison of distinct pointer types lacks a cast [-Werror]
> > >>    71 |  (void) (&__a == __d);   \
> > >>       |               ^~
> > >> drivers/net/ethernet/intel/e1000e/ethtool.c:582:6: note: in expansion of macro ‘check_add_overflow’
> > >>   582 |  if (check_add_overflow(eeprom->offset, eeprom->len, &total_len) ||
> > >>       |      ^~~~~~~~~~~~~~~~~~
> > >>
> > >> To fix this, change total_len and max_len from size_t to u32 in
> > >> e1000_set_eeprom().
> > >> The check_add_overflow() helper requires that the first two operands
> > >> and the pointer to the result (third operand) all have the same type.
> > >> On 64-bit builds, using size_t caused a mismatch with the u32 fields
> > >> eeprom->offset and eeprom->len, leading to type check failures.
> > >>
> > >> Fixes: ce8829d3d44b ("e1000e: fix heap overflow in e1000_set_eeprom")
> > >> Signed-off-by: Eliav Farber <farbere@amazon.com>
> > >> ---
> > >>  drivers/net/ethernet/intel/e1000e/ethtool.c | 2 +-
> > >>  1 file changed, 1 insertion(+), 1 deletion(-)
> > >>
> > >> diff --git a/drivers/net/ethernet/intel/e1000e/ethtool.c
> > >> b/drivers/net/ethernet/intel/e1000e/ethtool.c
> > >> index 4aca854783e2..584378291f3f 100644
> > >> --- a/drivers/net/ethernet/intel/e1000e/ethtool.c
> > >> +++ b/drivers/net/ethernet/intel/e1000e/ethtool.c
> > >> @@ -559,7 +559,7 @@ static int e1000_set_eeprom(struct net_device
> > >> *netdev,  {
> > >>       struct e1000_adapter *adapter = netdev_priv(netdev);
> > >>       struct e1000_hw *hw = &adapter->hw;
> > >> -     size_t total_len, max_len;
> > >> +     u32 total_len, max_len;
> > >>       u16 *eeprom_buff;
> > >>       int ret_val = 0;
> > >>       int first_word;
> > >> --
> > >> 2.47.3
> > >>
> > >
> > > Why is this not needed in Linus's tree?
> > Kernel 5.10.243 enforces the same type, but this enforcement is
> > absent from 5.15.192 and later:
> > /*
> >  * For simplicity and code hygiene, the fallback code below insists on
> >  * a, b and *d having the same type (similar to the min() and max()
> >  * macros), whereas gcc's type-generic overflow checkers accept
> >  * different types. Hence we don't just make check_add_overflow an
> >  * alias for __builtin_add_overflow, but add type checks similar to
> >  * below.
> >  */
> > #define check_add_overflow(a, b, d) __must_check_overflow(({  \
>
> Yeah, the min() build warning mess is slowly propagating back to older
> kernels over time as we take these types of fixes backwards.  I count 3
> such new warnings in the new 5.10 release, not just this single one.
>
> Overall, how about fixing this up so it doesn't happen anymore by
> backporting the min() logic instead?  That should solve this build
> warning, and keep it from happening again in the future?  I did that for
> newer kernel branches, but never got around to it for these.

I did backporting of 4 commits to bring include/linux/overflow.h in
line with v5.15.193 in order to pull commit 1d1ac8244c22 ("overflow:
Allow mixed type arguments").
I'll also check what can be done for include/linux/minmax.h.

---
Regards, Eliav