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Patch "net/mlx4_en: Fix type mismatch for 32-bit systems" has been added to the 4.9-stable tree

PATCH [email protected] 1 participant 1 message Dec 6, 2017

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This is a note to let you know that I've just added the patch titled

net/mlx4_en: Fix type mismatch for 32-bit systems

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
net-mlx4_en-fix-type-mismatch-for-32-bit-systems.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From foo@baz Wed Dec 6 17:39:55 CET 2017

From: Slava Shwartsman <[email protected]>
Date: Thu, 29 Dec 2016 18:37:12 +0200
Subject: net/mlx4_en: Fix type mismatch for 32-bit systems

From: Slava Shwartsman <[email protected]>

[ Upstream commit 61b6034c6cfdcb265bb453505c3d688e7567727a ]

is_power_of_2 expects unsigned long and we pass u64 max_val_cycles, this will be truncated on 32 bit systems, and the result is not what we were expecting.
div_u64 expects u32 as a second argument and we pass max_val_cycles_rounded which is u64 hence it will always be truncated. Fix was tested on both 64 and 32 bit systems and got same results for max_val_cycles and max_val_cycles_rounded.

Fixes 4850cf458157 ("net/mlx4_en: Resolve dividing by zero in 32-bit system")
---
 drivers/net/ethernet/mellanox/mlx4/en_clock.c |    8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)
drivers/net/ethernet/mellanox/mlx4/en_clock.c +2 -6
@@ -251,13 +251,9 @@ static u32 freq_to_shift(u16 freq)
 {
 	u32 freq_khz = freq * 1000;
 	u64 max_val_cycles = freq_khz * 1000 * MLX4_EN_WRAP_AROUND_SEC;
-	u64 tmp_rounded =
-		roundup_pow_of_two(max_val_cycles) > max_val_cycles ?
-		roundup_pow_of_two(max_val_cycles) - 1 : UINT_MAX;
-	u64 max_val_cycles_rounded = is_power_of_2(max_val_cycles + 1) ?
-		max_val_cycles : tmp_rounded;
+	u64 max_val_cycles_rounded = 1ULL << fls64(max_val_cycles - 1);
 	/* calculate max possible multiplier in order to fit in 64bit */
-	u64 max_mul = div_u64(0xffffffffffffffffULL, max_val_cycles_rounded);
+	u64 max_mul = div64_u64(ULLONG_MAX, max_val_cycles_rounded);
 
 	/* This comes from the reverse of clocksource_khz2mult */
 	return ilog2(div_u64(max_mul * freq_khz, 1000000));

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/net-mlx4_en-fix-type-mismatch-for-32-bit-systems.patch