Re: [PATCH 04/22] drm/tegra: Check for malformed offsets and sizes in the 'submit' IOCTL

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Just some comments on comments (?!). With those fixed,

Reviewed-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>

On 05/23/2017 03:14 AM, Dmitry Osipenko wrote:
If commands buffer claims a number of words that is higher than its BO can
fit, a kernel OOPS will be fired on the out-of-bounds BO access. This was
triggered by an opentegra Xorg driver that erroneously pushed too many
commands to the pushbuf.

The CMDA commands buffer address is 4 bytes aligned, so check its alignment.

CDMA


The maximum number of the CDMA gather fetches is 16383, add a check for it.

Add a sanity check for the relocations in a same way.

[   46.829393] Unable to handle kernel paging request at virtual address f09b2000
...
[<c04a3ba4>] (host1x_job_pin) from [<c04dfcd0>] (tegra_drm_submit+0x474/0x510)
[<c04dfcd0>] (tegra_drm_submit) from [<c04deea0>] (tegra_submit+0x50/0x6c)
[<c04deea0>] (tegra_submit) from [<c04c07c0>] (drm_ioctl+0x1e4/0x3ec)
[<c04c07c0>] (drm_ioctl) from [<c02541a0>] (do_vfs_ioctl+0x9c/0x8e4)
[<c02541a0>] (do_vfs_ioctl) from [<c0254a1c>] (SyS_ioctl+0x34/0x5c)
[<c0254a1c>] (SyS_ioctl) from [<c0107640>] (ret_fast_syscall+0x0/0x3c)

Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
Reviewed-by: Erik Faye-Lund <kusmabite@xxxxxxxxx>
---
  drivers/gpu/drm/tegra/drm.c | 48 +++++++++++++++++++++++++++++++++++++++++++++
  drivers/gpu/drm/tegra/gem.c |  5 -----
  drivers/gpu/drm/tegra/gem.h |  5 +++++
  3 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index f9282da94a1f..7e4559ec824d 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -26,6 +26,7 @@
  #define DRIVER_PATCHLEVEL 0
#define CARVEOUT_SZ SZ_64M
+#define CDMA_GATHER_FETCHES_MAX_NB 16383
struct tegra_drm_file {
  	struct idr contexts;
@@ -383,18 +384,41 @@ int tegra_drm_submit(struct tegra_drm_context *context,
  	while (num_cmdbufs) {
  		struct drm_tegra_cmdbuf cmdbuf;
  		struct host1x_bo *bo;
+		struct tegra_bo *obj;
+		u64 offset;
if (copy_from_user(&cmdbuf, cmdbufs, sizeof(cmdbuf))) {
  			err = -EFAULT;
  			goto fail;
  		}
+ /*
+		 * The maximum number of CDMA gather fetches is 16383, a higher
+		 * value means the words count is malformed.
+		 */
+		if (cmdbuf.words > CDMA_GATHER_FETCHES_MAX_NB) {
+			err = -EINVAL;
+			goto fail;
+		}
+
  		bo = host1x_bo_lookup(file, cmdbuf.handle);
  		if (!bo) {
  			err = -ENOENT;
  			goto fail;
  		}
+ offset = (u64)cmdbuf.offset + (u64)cmdbuf.words * sizeof(u32);
+		obj = host1x_to_tegra_bo(bo);
+
+		/*
+		 * The CDMA base address if 4-bytes aligned, unaligned offset

"Gather buffer base address must be", perhaps, as cmdbufs aren't used directly as CDMA buffers.

+		 * is malformed.
+		 */
+		if (offset & 3 || offset >= obj->gem.size) {
+			err = -EINVAL;
+			goto fail;
+		}
+
  		host1x_job_add_gather(job, bo, cmdbuf.words, cmdbuf.offset);
  		num_cmdbufs--;
  		cmdbufs++;
@@ -402,11 +426,35 @@ int tegra_drm_submit(struct tegra_drm_context *context,
/* copy and resolve relocations from submit */
  	while (num_relocs--) {
+		struct host1x_reloc *reloc;
+		struct tegra_bo *obj;
+
  		err = host1x_reloc_copy_from_user(&job->relocarray[num_relocs],
  						  &relocs[num_relocs], drm,
  						  file);
  		if (err < 0)
  			goto fail;
+
+		reloc = &job->relocarray[num_relocs];
+		obj = host1x_to_tegra_bo(reloc->cmdbuf.bo);
+
+		/*
+		 * The unaligned cmdbuf offset will cause an unaligned write

"An unaligned ..."

+		 * during of the relocations patching, corrupting the commands
+		 * stream.
+		 */
+		if (reloc->cmdbuf.offset & 3 ||
+		    reloc->cmdbuf.offset >= obj->gem.size) {
+			err = -EINVAL;
+			goto fail;
+		}
+
+		obj = host1x_to_tegra_bo(reloc->target.bo);
+
+		if (reloc->target.offset >= obj->gem.size) {
+			err = -EINVAL;
+			goto fail;
+		}
  	}
if (copy_from_user(job->waitchk, waitchks,
diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
index ca0d4439e97b..6a855b2f07fb 100644
--- a/drivers/gpu/drm/tegra/gem.c
+++ b/drivers/gpu/drm/tegra/gem.c
@@ -20,11 +20,6 @@
  #include "drm.h"
  #include "gem.h"
-static inline struct tegra_bo *host1x_to_tegra_bo(struct host1x_bo *bo)
-{
-	return container_of(bo, struct tegra_bo, base);
-}
-
  static void tegra_bo_put(struct host1x_bo *bo)
  {
  	struct tegra_bo *obj = host1x_to_tegra_bo(bo);
diff --git a/drivers/gpu/drm/tegra/gem.h b/drivers/gpu/drm/tegra/gem.h
index 6c5f12ac0087..8b32a6fd586d 100644
--- a/drivers/gpu/drm/tegra/gem.h
+++ b/drivers/gpu/drm/tegra/gem.h
@@ -52,6 +52,11 @@ static inline struct tegra_bo *to_tegra_bo(struct drm_gem_object *gem)
  	return container_of(gem, struct tegra_bo, gem);
  }
+static inline struct tegra_bo *host1x_to_tegra_bo(struct host1x_bo *bo)
+{
+	return container_of(bo, struct tegra_bo, base);
+}
+
  struct tegra_bo *tegra_bo_create(struct drm_device *drm, size_t size,
  				 unsigned long flags);
  struct tegra_bo *tegra_bo_create_with_handle(struct drm_file *file,

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