On Sat, 19 Mar 2016 14:58:21 +0100, Takashi Sakamoto wrote:
'struct snd_timer_gparams' includes some members with 'unsigned long', therefore its size differs depending on data models (ILP32/LP64). As a result, x86/x32 applications fail to execute ioctl(2) with SNDRV_TIMER_GPARAMS on x86_64 machine.
This commit fixes this bug by adding a pair of structure and ioctl command for the compatibility.
Signed-off-by: Takashi Sakamoto o-takashi@sakamocchi.jp
sound/core/timer_compat.c | 29 ++++++++++++++++++++++++++++- 1 file changed, 28 insertions(+), 1 deletion(-)
diff --git a/sound/core/timer_compat.c b/sound/core/timer_compat.c index 2e90822..5809387 100644 --- a/sound/core/timer_compat.c +++ b/sound/core/timer_compat.c @@ -22,6 +22,18 @@
#include <linux/compat.h>
+/*
- In LP64, 64 bit storage alignment is used, therefore the size of this
- structure is expanded to multiple of 8.
You can't say the 8 bytes alignment as LP64 generic. It rather depends on each architecture. Write something like "64bit storage alignment may be used (e.g. x86-64)".
But the size should be aligned to
- multiple of 4 for ILP32.
Actually, this isn't guaranteed so but practically seen, all 32bit architectures on Linux are at most 4 bytes alignment.
This is a reason to use 'packed' attribute.
- */
+struct snd_timer_gparams32 {
- struct snd_timer_id tid;
- u32 period_num;
- u32 period_den;
- unsigned char reserved[32];
+}__attribute__((packed));
struct snd_timer_info32 { u32 flags; s32 card; @@ -32,6 +44,19 @@ struct snd_timer_info32 { unsigned char reserved[64]; };
+static int snd_timer_user_gparams_compat(struct file *file,
struct snd_timer_gparams32 __user *user)+{
- struct snd_timer_gparams gparams;
- if (copy_from_user(&gparams, user,
sizeof(struct snd_timer_id) + sizeof(u32) + sizeof(u32)))return -EFAULT;- return snd_timer_user_gparams(file,
(struct snd_timer_gparams __user *)&gparams);
This is not correct in two ways:
- You didn't convert the data to the 64bit struct. So the passed values are garbled.
- Passing the instance on the stack as a user pointer is broken (unless you do some hacks).
For the first, you'd need to copy each field one by one. For the latter, snd_timer_user_gparams() needs to be split to two version, one for kernel pointer and one for user pointer with copy_from_user().
thanks,
Takashi