lkml.org 
[lkml]   [2016]   [Nov]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[patch] ALSA: emu10k1: shift wrapping bug in snd_emu10k1_ptr_read()
Static analysis says "size" is a number 0-63.  So we really want to be
doing the shift as a u64 and not a int type. Presumably "size" is never
actually more than 31 otherwise the shift wrap would have been detected
in testing. The "mask" is a u32 so we only care about the bottom 32
bits which also implies that "size" is less than 32.

This code pre-dates git. I haven't tested this change, it's to fix a
static analysis warning. I can't think that shift wrapping is the
correct behavior so presumably this change is harmless but it definitely
changes how the code works when size is larger than 32.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/sound/pci/emu10k1/io.c b/sound/pci/emu10k1/io.c
index 706b4f0..fd204f3 100644
--- a/sound/pci/emu10k1/io.c
+++ b/sound/pci/emu10k1/io.c
@@ -46,7 +46,7 @@ unsigned int snd_emu10k1_ptr_read(struct snd_emu10k1 * emu, unsigned int reg, un

size = (reg >> 24) & 0x3f;
offset = (reg >> 16) & 0x1f;
- mask = ((1 << size) - 1) << offset;
+ mask = ((1ULL << size) - 1) << offset;

spin_lock_irqsave(&emu->emu_lock, flags);
outl(regptr, emu->port + PTR);
@@ -81,7 +81,7 @@ void snd_emu10k1_ptr_write(struct snd_emu10k1 *emu, unsigned int reg, unsigned i

size = (reg >> 24) & 0x3f;
offset = (reg >> 16) & 0x1f;
- mask = ((1 << size) - 1) << offset;
+ mask = ((1ULL << size) - 1) << offset;
data = (data << offset) & mask;

spin_lock_irqsave(&emu->emu_lock, flags);
\
 
 \ /
  Last update: 2016-11-24 12:25    [W:0.049 / U:0.540 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site