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drm/i915/gem: Serialise debugfs i915_gem_objects with ctx->mutex

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Since the debugfs may peek into the GEM contexts as the corresponding
client/fd is being closed, we may try and follow a dangling pointer.
However, the context closure itself is serialised with the ctx->mutex,
so if we hold that mutex as we inspect the state coupled in the context,
we know the pointers within the context are stable and will remain valid
as we inspect their tables.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: CQ Tang <cq.tang@intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200723172119.17649-3-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson
2020-07-23 18:21:19 +01:00
parent 5ae26012a1
commit 102f5aa491
1 changed files with 2 additions and 0 deletions
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2
drivers/gpu/drm/i915/i915_debugfs.c
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@@ -326,6 +326,7 @@ static void print_context_stats(struct seq_file *m,
}
i915_gem_context_unlock_engines(ctx);
mutex_lock(&ctx->mutex);
if (!IS_ERR_OR_NULL(ctx->file_priv)) {
struct file_stats stats = {
.vm = rcu_access_pointer(ctx->vm),
@@ -346,6 +347,7 @@ static void print_context_stats(struct seq_file *m,
print_file_stats(m, name, stats);
}
mutex_unlock(&ctx->mutex);
spin_lock(&i915->gem.contexts.lock);
list_safe_reset_next(ctx, cn, link);