| Message ID | 1416841607-8418-1-git-send-email-luis.henriques@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c index d7d5c8af92b9..6d4456898007 100644 --- a/drivers/firewire/core-cdev.c +++ b/drivers/firewire/core-cdev.c @@ -1637,8 +1637,7 @@ static int dispatch_ioctl(struct client *client, _IOC_SIZE(cmd) > sizeof(buffer)) return -ENOTTY; - if (_IOC_DIR(cmd) == _IOC_READ) - memset(&buffer, 0, _IOC_SIZE(cmd)); + memset(&buffer, 0, sizeof(buffer)); if (_IOC_DIR(cmd) & _IOC_WRITE) if (copy_from_user(&buffer, arg, _IOC_SIZE(cmd)))
This is a note to let you know that I have just added a patch titled firewire: cdev: prevent kernel stack leaking into ioctl arguments to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue This patch is scheduled to be released in version 3.16.7-ckt2. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.16.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From f3b29d982301704429e213ddee59fbaa1b644989 Mon Sep 17 00:00:00 2001 From: Stefan Richter <stefanr@s5r6.in-berlin.de> Date: Tue, 11 Nov 2014 17:16:44 +0100 Subject: firewire: cdev: prevent kernel stack leaking into ioctl arguments commit eaca2d8e75e90a70a63a6695c9f61932609db212 upstream. Found by the UC-KLEE tool: A user could supply less input to firewire-cdev ioctls than write- or write/read-type ioctl handlers expect. The handlers used data from uninitialized kernel stack then. This could partially leak back to the user if the kernel subsequently generated fw_cdev_event_'s (to be read from the firewire-cdev fd) which notably would contain the _u64 closure field which many of the ioctl argument structures contain. The fact that the handlers would act on random garbage input is a lesser issue since all handlers must check their input anyway. The fix simply always null-initializes the entire ioctl argument buffer regardless of the actual length of expected user input. That is, a runtime overhead of memset(..., 40) is added to each firewirew-cdev ioctl() call. [Comment from Clemens Ladisch: This part of the stack is most likely to be already in the cache.] Remarks: - There was never any leak from kernel stack to the ioctl output buffer itself. IOW, it was not possible to read kernel stack by a read-type or write/read-type ioctl alone; the leak could at most happen in combination with read()ing subsequent event data. - The actual expected minimum user input of each ioctl from include/uapi/linux/firewire-cdev.h is, in bytes: [0x00] = 32, [0x05] = 4, [0x0a] = 16, [0x0f] = 20, [0x14] = 16, [0x01] = 36, [0x06] = 20, [0x0b] = 4, [0x10] = 20, [0x15] = 20, [0x02] = 20, [0x07] = 4, [0x0c] = 0, [0x11] = 0, [0x16] = 8, [0x03] = 4, [0x08] = 24, [0x0d] = 20, [0x12] = 36, [0x17] = 12, [0x04] = 20, [0x09] = 24, [0x0e] = 4, [0x13] = 40, [0x18] = 4. Reported-by: David Ramos <daramos@stanford.edu> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/firewire/core-cdev.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) -- 2.1.0