[PATCH AUTOSEL 4.19 25/31] stmmac: fix pointer check after utilization in stmmac_interrupt

[PATCH AUTOSEL 4.19 25/31] stmmac: fix pointer check after utilization in stmmac_interrupt

[Sasha Levin]

From: Maxim Petrov <mmrmaximuzz@gmail.com>

[ Upstream commit f42234ffd531ca6b13d9da02faa60b72eccf8334 ]

The paranoidal pointer check in IRQ handler looks very strange - it
really protects us only against bogus drivers which request IRQ line
with null pointer dev_id. However, the code fragment is incorrect
because the dev pointer is used before the actual check which leads
to undefined behavior. Remove the check to avoid confusing people
with incorrect code.

Signed-off-by: Maxim Petrov <mmrmaximuzz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 9c7b1d8e82204..c41879a955b57 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -3684,7 +3684,7 @@ static int stmmac_set_features(struct net_device *netdev,
 /**
  *  stmmac_interrupt - main ISR
  *  @irq: interrupt number.
- *  @dev_id: to pass the net device pointer.
+ *  @dev_id: to pass the net device pointer (must be valid).
  *  Description: this is the main driver interrupt service routine.
  *  It can call:
  *  o DMA service routine (to manage incoming frame reception and transmission
@@ -3708,11 +3708,6 @@ static irqreturn_t stmmac_interrupt(int irq, void *dev_id)
 	if (priv->irq_wake)
 		pm_wakeup_event(priv->device, 0);
 
-	if (unlikely(!dev)) {
-		netdev_err(priv->dev, "%s: invalid dev pointer\n", __func__);
-		return IRQ_NONE;
-	}
-
 	/* Check if adapter is up */
 	if (test_bit(STMMAC_DOWN, &priv->state))
 		return IRQ_HANDLED;
-- 
2.20.1


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[PATCH AUTOSEL 4.19 28/31] ARM: futex: Address build warning

[Sasha Levin]

From: Thomas Gleixner <tglx@linutronix.de>

[ Upstream commit 8101b5a1531f3390b3a69fa7934c70a8fd6566ad ]

Stephen reported the following build warning on a ARM multi_v7_defconfig
build with GCC 9.2.1:

kernel/futex.c: In function 'do_futex':
kernel/futex.c:1676:17: warning: 'oldval' may be used uninitialized in this function [-Wmaybe-uninitialized]
 1676 |   return oldval == cmparg;
      |          ~~~~~~~^~~~~~~~~
kernel/futex.c:1652:6: note: 'oldval' was declared here
 1652 |  int oldval, ret;
      |      ^~~~~~

introduced by commit a08971e9488d ("futex: arch_futex_atomic_op_inuser()
calling conventions change").

While that change should not make any difference it confuses GCC which
fails to work out that oldval is not referenced when the return value is
not zero.

GCC fails to properly analyze arch_futex_atomic_op_inuser(). It's not the
early return, the issue is with the assembly macros. GCC fails to detect
that those either set 'ret' to 0 and set oldval or set 'ret' to -EFAULT
which makes oldval uninteresting. The store to the callsite supplied oldval
pointer is conditional on ret == 0.

The straight forward way to solve this is to make the store unconditional.

Aside of addressing the build warning this makes sense anyway because it
removes the conditional from the fastpath. In the error case the stored
value is uninteresting and the extra store does not matter at all.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/87pncao2ph.fsf@nanos.tec.linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/arm/include/asm/futex.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/futex.h b/arch/arm/include/asm/futex.h
index ffebe7b7a5b74..91ca80035fc42 100644
--- a/arch/arm/include/asm/futex.h
+++ b/arch/arm/include/asm/futex.h
@@ -163,8 +163,13 @@ arch_futex_atomic_op_inuser(int op, int oparg, int *oval, u32 __user *uaddr)
 	preempt_enable();
 #endif
 
-	if (!ret)
-		*oval = oldval;
+	/*
+	 * Store unconditionally. If ret != 0 the extra store is the least
+	 * of the worries but GCC cannot figure out that __futex_atomic_op()
+	 * is either setting ret to -EFAULT or storing the old value in
+	 * oldval which results in a uninitialized warning at the call site.
+	 */
+	*oval = oldval;
 
 	return ret;
 }
-- 
2.20.1


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