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Commit 84d2099e authored by Erick Reyes's avatar Erick Reyes Committed by Greg Kroah-Hartman
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ALSA: info: Check for integer overflow in snd_info_entry_write() 



Commit 4adb7bcbcb69 ("ALSA: core: Use seq_file for text proc file
reads") heavily refactored ALSA procfs and fixed the overflow as
a side-effect, so this fix only applies to kernels < 4.2 and
there is no upstream equivalent

snd_info_entry_write() resizes the buffer with an unsigned long
size argument that gets truncated because resize_info_buffer()
takes the size parameter as an unsigned int. On 64-bit kernels,
this causes the following copy_to_user() to write out-of-bounds
if (pos + count) can't be represented by an unsigned int.

Signed-off-by: default avatarSiqi Lin <siqilin@google.com>
Signed-off-by: default avatarErick Reyes <erickreyes@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 208255c7

sound/core/info.c

+3 −1
Original line number Diff line number Diff line
@@ -253,6 +253,7 @@ static ssize_t snd_info_entry_write(struct file *file, const char __user *buffer 
	struct snd_info_buffer *buf;

	ssize_t size = 0;

	loff_t pos;

	unsigned long realloc_size;



	data = file->private_data;

	if (snd_BUG_ON(!data))
@@ -261,7 +262,8 @@ static ssize_t snd_info_entry_write(struct file *file, const char __user *buffer 
	pos = *offset;

	if (pos < 0 || (long) pos != pos || (ssize_t) count < 0)

		return -EIO;

	if ((unsigned long) pos + (unsigned long) count < (unsigned long) pos)

	realloc_size = (unsigned long) pos + (unsigned long) count;

	if (realloc_size < (unsigned long) pos || realloc_size > UINT_MAX)

		return -EIO;

	switch (entry->content) {

	case SNDRV_INFO_CONTENT_TEXT: