linux-kernel - [PATCH v2] drm/i915: use strscpy() to avoid buffer overrun

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Message-Id: <20210916122649.12691-1-tim.gardner@canonical.com>
Date:   Thu, 16 Sep 2021 06:26:49 -0600
From:   Tim Gardner <tim.gardner@...onical.com>
To:     intel-gfx@...ts.freedesktop.org
Cc:     tim.gardner@...onical.com,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] drm/i915: use strscpy() to avoid buffer overrun

In capture_vma() Coverity complains of a possible buffer overrun. Even
though this is a static function where all call sites can be checked,
limiting the copy length could save some future grief.

CID 93300 (#1 of 1): Copy into fixed size buffer (STRING_OVERFLOW)
4. fixed_size_dest: You might overrun the 16-character fixed-size string c->name
   by copying name without checking the length.
5. parameter_as_source: Note: This defect has an elevated risk because the
   source argument is a parameter of the current function.
1326        strcpy(c->name, name);

Fix any possible overflows by using strscpy() which guarantees NULL termination.

Also correct 2 other strcpy() call sites with the same potential for Coverity
warnings or overruns.

v2 - Change $SUBJECT from "drm/i915: zero fill vma name buffer"
     Use strscpy() instead of strncpy(). Its a much simpler change.

Cc: Jani Nikula <jani.nikula@...ux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@...el.com>
Cc: David Airlie <airlied@...ux.ie>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: intel-gfx@...ts.freedesktop.org
Cc: dri-devel@...ts.freedesktop.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
---
 drivers/gpu/drm/i915/i915_gpu_error.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 9cf6ac575de1..7f246f51959d 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1015,7 +1015,7 @@ i915_vma_coredump_create(const struct intel_gt *gt,
 		return NULL;
 	}
 
-	strcpy(dst->name, name);
+	strscpy(dst->name, name, sizeof(dst->name));
 	dst->next = NULL;
 
 	dst->gtt_offset = vma->node.start;
@@ -1279,7 +1279,7 @@ static bool record_context(struct i915_gem_context_coredump *e,
 	rcu_read_lock();
 	task = pid_task(ctx->pid, PIDTYPE_PID);
 	if (task) {
-		strcpy(e->comm, task->comm);
+		strscpy(e->comm, task->comm, sizeof(e->comm));
 		e->pid = task->pid;
 	}
 	rcu_read_unlock();
@@ -1323,7 +1323,7 @@ capture_vma(struct intel_engine_capture_vma *next,
 		return next;
 	}
 
-	strcpy(c->name, name);
+	strscpy(c->name, name, sizeof(c->name));
 	c->vma = vma; /* reference held while active */
 
 	c->next = next;
-- 
2.33.0