This is a note to let you know that I've just added the patch titled
drm/i915: Fix potential context UAFs
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
drm-i915-fix-potential-context-uafs.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From afce71ff6daa9c0f852df0727fe32c6fb107f0fa Mon Sep 17 00:00:00 2001
From: Rob Clark <robdclark@xxxxxxxxxxxx>
Date: Tue, 3 Jan 2023 15:49:46 -0800
Subject: drm/i915: Fix potential context UAFs
From: Rob Clark <robdclark@xxxxxxxxxxxx>
commit afce71ff6daa9c0f852df0727fe32c6fb107f0fa upstream.
gem_context_register() makes the context visible to userspace, and which
point a separate thread can trigger the I915_GEM_CONTEXT_DESTROY ioctl.
So we need to ensure that nothing uses the ctx ptr after this. And we
need to ensure that adding the ctx to the xarray is the *last* thing
that gem_context_register() does with the ctx pointer.
Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
Fixes: eb4dedae920a ("drm/i915/gem: Delay tracking the GEM context until it is registered")
Fixes: a4c1cdd34e2c ("drm/i915/gem: Delay context creation (v3)")
Fixes: 49bd54b390c2 ("drm/i915: Track all user contexts per client")
Cc: <stable@xxxxxxxxxxxxxxx> # v5.10+
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
[tursulin: Stable and fixes tags add/tidy.]
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20230103234948.1218393-1-robdclark@xxxxxxxxx
(cherry picked from commit bed4b455cf5374e68879be56971c1da563bcd90c)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_context.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1688,6 +1688,10 @@ void i915_gem_init__contexts(struct drm_
init_contexts(&i915->gem.contexts);
}
+/*
+ * Note that this implicitly consumes the ctx reference, by placing
+ * the ctx in the context_xa.
+ */
static void gem_context_register(struct i915_gem_context *ctx,
struct drm_i915_file_private *fpriv,
u32 id)
@@ -1703,10 +1707,6 @@ static void gem_context_register(struct
snprintf(ctx->name, sizeof(ctx->name), "%s[%d]",
current->comm, pid_nr(ctx->pid));
- /* And finally expose ourselves to userspace via the idr */
- old = xa_store(&fpriv->context_xa, id, ctx, GFP_KERNEL);
- WARN_ON(old);
-
spin_lock(&ctx->client->ctx_lock);
list_add_tail_rcu(&ctx->client_link, &ctx->client->ctx_list);
spin_unlock(&ctx->client->ctx_lock);
@@ -1714,6 +1714,10 @@ static void gem_context_register(struct
spin_lock(&i915->gem.contexts.lock);
list_add_tail(&ctx->link, &i915->gem.contexts.list);
spin_unlock(&i915->gem.contexts.lock);
+
+ /* And finally expose ourselves to userspace via the idr */
+ old = xa_store(&fpriv->context_xa, id, ctx, GFP_KERNEL);
+ WARN_ON(old);
}
int i915_gem_context_open(struct drm_i915_private *i915,
@@ -2199,14 +2203,22 @@ finalize_create_context_locked(struct dr
if (IS_ERR(ctx))
return ctx;
+ /*
+ * One for the xarray and one for the caller. We need to grab
+ * the reference *prior* to making the ctx visble to userspace
+ * in gem_context_register(), as at any point after that
+ * userspace can try to race us with another thread destroying
+ * the context under our feet.
+ */
+ i915_gem_context_get(ctx);
+
gem_context_register(ctx, file_priv, id);
old = xa_erase(&file_priv->proto_context_xa, id);
GEM_BUG_ON(old != pc);
proto_context_close(file_priv->dev_priv, pc);
- /* One for the xarray and one for the caller */
- return i915_gem_context_get(ctx);
+ return ctx;
}
struct i915_gem_context *
Patches currently in stable-queue which might be from robdclark@xxxxxxxxxxxx are
queue-6.1/drm-virtio-fix-gem-handle-creation-uaf.patch
queue-6.1/drm-i915-fix-potential-context-uafs.patch
