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: Siqi Lin siqilin@google.com Signed-off-by: Erick Reyes erickreyes@google.com --- sound/core/info.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/core/info.c b/sound/core/info.c index 9f404e965ea2..08832c973a53 100644 --- a/sound/core/info.c +++ b/sound/core/info.c @@ -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: