[media] media: s5p-mfc fix invalid memory access from s5p_mfc_release()

If s5p_mfc_release() runs after s5p_mfc_remove(), the former will access
invalid s5p_mfc_dev pointer saved in the s5p_mfc_ctx and runs into kernel
paging request errors.

Clear ctx dev pointer in s5p_mfc_remove() and change s5p_mfc_release() to
avoid work that requires ctx->dev.

odroid kernel: Unable to handle kernel paging request at virtual address
    f17c1104
odroid kernel: pgd = ebca4000
odroid kernel: [f17c1104] *pgd=6e23d811, *pte=00000000, *ppte=00000000
odroid kernel: Internal error: Oops: 807 [#1] PREEMPT SMP ARM
odroid kernel: Modules linked in: cpufreq_userspace cpufreq_powersave
    cpufreq_conservative s5p_mfc s5p_jpeg v4l2_mem2mem
    videobuf2_dma_contig videobuf2_memops videobuf2_v4l2 videobuf2_core
    v4l2_common videodev media
odroid kernel: Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
odroid kernel: task: c2241400 ti: e7018000 task.ti: e7018000
odroid kernel: PC is at s5p_mfc_reset+0x40/0x28c [s5p_mfc]
odroid kernel: LR is at s5p_mfc_reset+0x34/0x28c [s5p_mfc]
odroid kernel: pc : [<bf15bfbc>]    lr : [<bf15bfb0>] psr: 60010013
odroid kernel: [<bf15bfbc>] (s5p_mfc_reset [s5p_mfc]) from [<bf15c62c>]
    (s5p_mfc_deinit_hw+0x14/0x3c [s5p_mfc])
odroid kernel: [<bf15c62c>] (s5p_mfc_deinit_hw [s5p_mfc]) from [<bf155958>]
    (s5p_mfc_release+0xac/0x1c4 [s5p_mfc])
odroid kernel: [<bf155958>] (s5p_mfc_release [s5p_mfc]) from [<bf021344>]
    (v4l2_release+0x38/0x74 [videodev])
odroid kernel: [<bf021344>] (v4l2_release [videodev]) from [<c01e4274>]
    (__fput+0x80/0x1c8)
odroid kernel: [<c01e4274>] (__fput) from [<c0135c58>]
    (task_work_run+0x94/0xc8)
odroid kernel: [<c0135c58>] (task_work_run) from [<c010a9d4>]
    (do_work_pending+0x7c/0xa4)
odroid kernel: [<c010a9d4>] (do_work_pending) from [<c0107794>]
    (slow_work_pending+0xc/0x20)
odroid kernel: Code: eb3edacc e5953078 e3a06000 e2833c11 (e5836004)

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Tested-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

diff --git a/drivers/media/platform/s5p-mfc/s5p_mfc.c b/drivers/media/platform/s5p-mfc/s5p_mfc.c
index e3f104f..69c91c0 100644 (file)
--- a/drivers/media/platform/s5p-mfc/s5p_mfc.c
+++ b/drivers/media/platform/s5p-mfc/s5p_mfc.c
@@ -924,39 +924,50 @@ static int s5p_mfc_release(struct file *file)
        struct s5p_mfc_ctx *ctx = fh_to_ctx(file->private_data);
        struct s5p_mfc_dev *dev = ctx->dev;
 
+       /* if dev is null, do cleanup that doesn't need dev */
        mfc_debug_enter();
-       mutex_lock(&dev->mfc_mutex);
+       if (dev)
+               mutex_lock(&dev->mfc_mutex);
        s5p_mfc_clock_on();
        vb2_queue_release(&ctx->vq_src);
        vb2_queue_release(&ctx->vq_dst);
-       /* Mark context as idle */
-       clear_work_bit_irqsave(ctx);
-       /* If instance was initialised and not yet freed,
-        * return instance and free resources */
-       if (ctx->state != MFCINST_FREE && ctx->state != MFCINST_INIT) {
-               mfc_debug(2, "Has to free instance\n");
-               s5p_mfc_close_mfc_inst(dev, ctx);
-       }
-       /* hardware locking scheme */
-       if (dev->curr_ctx == ctx->num)
-               clear_bit(0, &dev->hw_lock);
-       dev->num_inst--;
-       if (dev->num_inst == 0) {
-               mfc_debug(2, "Last instance\n");
-               s5p_mfc_deinit_hw(dev);
-               del_timer_sync(&dev->watchdog_timer);
-               if (s5p_mfc_power_off() < 0)
-                       mfc_err("Power off failed\n");
+       if (dev) {
+               /* Mark context as idle */
+               clear_work_bit_irqsave(ctx);
+               /*
+                * If instance was initialised and not yet freed,
+                * return instance and free resources
+               */
+               if (ctx->state != MFCINST_FREE && ctx->state != MFCINST_INIT) {
+                       mfc_debug(2, "Has to free instance\n");
+                       s5p_mfc_close_mfc_inst(dev, ctx);
+               }
+               /* hardware locking scheme */
+               if (dev->curr_ctx == ctx->num)
+                       clear_bit(0, &dev->hw_lock);
+               dev->num_inst--;
+               if (dev->num_inst == 0) {
+                       mfc_debug(2, "Last instance\n");
+                       s5p_mfc_deinit_hw(dev);
+                       del_timer_sync(&dev->watchdog_timer);
+                       if (s5p_mfc_power_off() < 0)
+                               mfc_err("Power off failed\n");
+               }
        }
        mfc_debug(2, "Shutting down clock\n");
        s5p_mfc_clock_off();
-       dev->ctx[ctx->num] = NULL;
+       if (dev)
+               dev->ctx[ctx->num] = NULL;
        s5p_mfc_dec_ctrls_delete(ctx);
        v4l2_fh_del(&ctx->fh);
-       v4l2_fh_exit(&ctx->fh);
+       /* vdev is gone if dev is null */
+       if (dev)
+               v4l2_fh_exit(&ctx->fh);
        kfree(ctx);
        mfc_debug_leave();
-       mutex_unlock(&dev->mfc_mutex);
+       if (dev)
+               mutex_unlock(&dev->mfc_mutex);
+
        return 0;
 }
 
@@ -1298,9 +1309,26 @@ err_dma:
 static int s5p_mfc_remove(struct platform_device *pdev)
 {
        struct s5p_mfc_dev *dev = platform_get_drvdata(pdev);
+       struct s5p_mfc_ctx *ctx;
+       int i;
 
        v4l2_info(&dev->v4l2_dev, "Removing %s\n", pdev->name);
 
+       /*
+        * Clear ctx dev pointer to avoid races between s5p_mfc_remove()
+        * and s5p_mfc_release() and s5p_mfc_release() accessing ctx->dev
+        * after s5p_mfc_remove() is run during unbind.
+       */
+       mutex_lock(&dev->mfc_mutex);
+       for (i = 0; i < MFC_NUM_CONTEXTS; i++) {
+               ctx = dev->ctx[i];
+               if (!ctx)
+                       continue;
+               /* clear ctx->dev */
+               ctx->dev = NULL;
+       }
+       mutex_unlock(&dev->mfc_mutex);
+
        del_timer_sync(&dev->watchdog_timer);
        flush_workqueue(dev->watchdog_workqueue);
        destroy_workqueue(dev->watchdog_workqueue);