From: Gustavo A. R. Silva Date: Tue, 16 Oct 2018 09:55:49 +0000 (+0200) Subject: drm/bufs: Fix Spectre v1 vulnerability X-Git-Tag: Ubuntu-4.15.0-49.53~35 X-Git-Url: https://git.proxmox.com/?p=mirror_ubuntu-bionic-kernel.git;a=commitdiff_plain;h=692898803a8b25ebaef16226933a837b7b662942 drm/bufs: Fix Spectre v1 vulnerability idx can be indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability. This issue was detected with the help of Smatch: drivers/gpu/drm/drm_bufs.c:1420 drm_legacy_freebufs() warn: potential spectre issue 'dma->buflist' [r] (local cap) Fix this by sanitizing idx before using it to index dma->buflist Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 Signed-off-by: Gustavo A. R. Silva Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20181016095549.GA23586@embeddedor.com CVE-2017-5753 (cherry picked from commit a37805098900a6e73a55b3a43b7d3bcd987bb3f4) Signed-off-by: Juerg Haefliger Acked-by: Stefan Bader Acked-by: Kleber Sacilotto de Souza Signed-off-by: Stefan Bader --- diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c index 1ee84dd802d4..0f05b8d8fefa 100644 --- a/drivers/gpu/drm/drm_bufs.c +++ b/drivers/gpu/drm/drm_bufs.c @@ -36,6 +36,8 @@ #include #include "drm_legacy.h" +#include + static struct drm_map_list *drm_find_matching_map(struct drm_device *dev, struct drm_local_map *map) { @@ -1417,6 +1419,7 @@ int drm_legacy_freebufs(struct drm_device *dev, void *data, idx, dma->buf_count - 1); return -EINVAL; } + idx = array_index_nospec(idx, dma->buf_count); buf = dma->buflist[idx]; if (buf->file_priv != file_priv) { DRM_ERROR("Process %d freeing buffer not owned\n",