From 1147c9cdd0f60f09a98702a9f865176af18a989f Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Tue, 2 Dec 2008 13:38:47 +1000 Subject: [PATCH] drm: fix leak of uninitialized data to userspace ...so drm_getunique() is trying to copy some uninitialized data to userspace. The ECX register contains the number of words that are left to copy -- so there are 5 * 4 = 20 bytes left. The offset of the first uninitialized byte (counting from the start of the string) is also 20 (i.e. 0xf65d2294&((1 << 5)-1) == 20). So somebody tried to copy 40 bytes when the string was only 19 long. In drm_set_busid() we have this code: dev->unique_len = 40; dev->unique = drm_alloc(dev->unique_len + 1, DRM_MEM_DRIVER); ... len = snprintf(dev->unique, dev->unique_len, pci:%04x:%02x:%02x.%d", ...so it seems that dev->unique is never updated to reflect the actual length of the string. The remaining bytes (20 in this case) are random uninitialized bytes that are copied into userspace. This patch fixes the problem by setting dev->unique_len after the snprintf(). airlied- I've had to fix this up to store the alloced size so we have it for drm_free later. Reported-by: Sitsofe Wheeler Signed-off-by: Vegard Nossum Signed-off-by: Dave Airlie --- drivers/gpu/drm/drm_ioctl.c | 10 +++++++--- drivers/gpu/drm/drm_stub.c | 2 +- include/drm/drmP.h | 1 + 3 files changed, 9 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index e35126a35093..1fad76289e66 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -92,7 +92,8 @@ int drm_setunique(struct drm_device *dev, void *data, return -EINVAL; master->unique_len = u->unique_len; - master->unique = drm_alloc(u->unique_len + 1, DRM_MEM_DRIVER); + master->unique_size = u->unique_len + 1; + master->unique = drm_alloc(master->unique_size, DRM_MEM_DRIVER); if (!master->unique) return -ENOMEM; if (copy_from_user(master->unique, u->unique, master->unique_len)) @@ -136,7 +137,8 @@ static int drm_set_busid(struct drm_device *dev, struct drm_file *file_priv) return -EBUSY; master->unique_len = 40; - master->unique = drm_alloc(master->unique_len + 1, DRM_MEM_DRIVER); + master->unique_size = master->unique_len; + master->unique = drm_alloc(master->unique_size, DRM_MEM_DRIVER); if (master->unique == NULL) return -ENOMEM; @@ -145,8 +147,10 @@ static int drm_set_busid(struct drm_device *dev, struct drm_file *file_priv) dev->pdev->bus->number, PCI_SLOT(dev->pdev->devfn), PCI_FUNC(dev->pdev->devfn)); - if (len > master->unique_len) + if (len >= master->unique_len) DRM_ERROR("buffer overflow"); + else + master->unique_len = len; dev->devname = drm_alloc(strlen(dev->driver->pci_driver.name) + master->unique_len + diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c index 0f24c2dcd517..f7985c303cb0 100644 --- a/drivers/gpu/drm/drm_stub.c +++ b/drivers/gpu/drm/drm_stub.c @@ -117,7 +117,7 @@ static void drm_master_destroy(struct kref *kref) dev->driver->master_destroy(dev, master); if (master->unique) { - drm_free(master->unique, strlen(master->unique) + 1, DRM_MEM_DRIVER); + drm_free(master->unique, master->unique_size, DRM_MEM_DRIVER); master->unique = NULL; master->unique_len = 0; } diff --git a/include/drm/drmP.h b/include/drm/drmP.h index 4c6e8298b424..c9cc618dbcfc 100644 --- a/include/drm/drmP.h +++ b/include/drm/drmP.h @@ -627,6 +627,7 @@ struct drm_master { char *unique; /**< Unique identifier: e.g., busid */ int unique_len; /**< Length of unique field */ + int unique_size; /**< amount allocated */ int blocked; /**< Blocked due to VC switch? */ -- 2.39.5