[alsa-devel] [PATCH] 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: 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:
On Wed, Aug 15, 2018 at 05:55:48PM -0700, Erick Reyes wrote:
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
Thanks for the patch. I'll queue this up for 3.18.
greg k-h
This is a note to let you know that I've just added the patch titled
ALSA: info: Check for integer overflow in snd_info_entry_write()
to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summ...
The filename of the patch is: alsa-info-check-for-integer-overflow-in-snd_info_entry_write.patch and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From erickreyes@google.com Thu Aug 16 12:07:22 2018
From: Erick Reyes erickreyes@google.com Date: Wed, 15 Aug 2018 17:55:48 -0700 Subject: ALSA: info: Check for integer overflow in snd_info_entry_write() To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Jaroslav Kysela perex@perex.cz, Takashi Iwai tiwai@suse.com, kernel-team@android.com, Vinod Koul vkoul@kernel.org, Joe Perches joe@perches.com, Al Viro viro@zeniv.linux.org.uk, alsa-devel@alsa-project.org, Erick Reyes erickreyes@google.com, Siqi Lin siqilin@google.com Message-ID: 20180816005548.151269-1-erickreyes@google.com
From: Erick Reyes erickreyes@google.com
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- sound/core/info.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/sound/core/info.c +++ b/sound/core/info.c @@ -253,6 +253,7 @@ static ssize_t snd_info_entry_write(stru 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(stru 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:
Patches currently in stable-queue which might be from erickreyes@google.com are
queue-3.18/alsa-info-check-for-integer-overflow-in-snd_info_entry_write.patch
participants (3)
-
Erick Reyes -
Greg KH -
gregkh＠linuxfoundation.org