[Mesa-dev] [PATCH v7 1/2] gallium/winsys/kms: Fix possible leak in map/unmap.

[Lepton Wu]

If user calls map twice for kms_sw_displaytarget, the first mapped
buffer could get leaked. Instead of calling mmap every time, just
reuse previous mapping. Since user could map same displaytarget with
different flags, we have to keep two different pointers, one for rw
mapping and one for ro mapping. Also introduce reference count for
mapped buffer so we can unmap them at right time.

v2:
 - avoid duplicated mapping and leaked mapping (Tomasz)
v3:
 - split from larger patch (Emil)
v4:
 - remove munmap from dt_destory (Emil)
v5:
 - introduce reference count for mapping (Tomasz)
 - add back munmap in dt_destory
v6:
 - remove change-id in commit message (Tomasz)
v7:
 - remove munmap from dt_destory again (Emil)
 - add revision history in commit message (Emil)

Reviewed-by: Emil Velikov <emil.veli...@collabora.com>
Reviewed-by: Tomasz Figa <tf...@chromium.org>
Signed-off-by: Lepton Wu <lep...@chromium.org>
---
 .../winsys/sw/kms-dri/kms_dri_sw_winsys.c     | 38 +++++++++++++++----
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/src/gallium/winsys/sw/kms-dri/kms_dri_sw_winsys.c 
b/src/gallium/winsys/sw/kms-dri/kms_dri_sw_winsys.c
index 22e1c936ac..f7bad06edb 100644
--- a/src/gallium/winsys/sw/kms-dri/kms_dri_sw_winsys.c
+++ b/src/gallium/winsys/sw/kms-dri/kms_dri_sw_winsys.c
@@ -70,8 +70,10 @@ struct kms_sw_displaytarget
 
    uint32_t handle;
    void *mapped;
+   void *ro_mapped;
 
    int ref_count;
+   int map_count;
    struct list_head link;
 };
 
@@ -170,6 +172,10 @@ kms_sw_displaytarget_destroy(struct sw_winsys *ws,
    if (kms_sw_dt->ref_count > 0)
       return;
 
+   if (kms_sw_dt->map_count > 0) {
+      DEBUG_PRINT("KMS-DEBUG: leaked map buffer %u\n", kms_sw_dt->handle);
+   }
+
    memset(&destroy_req, 0, sizeof destroy_req);
    destroy_req.handle = kms_sw_dt->handle;
    drmIoctl(kms_sw->fd, DRM_IOCTL_MODE_DESTROY_DUMB, &destroy_req);
@@ -198,16 +204,21 @@ kms_sw_displaytarget_map(struct sw_winsys *ws,
       return NULL;
 
    prot = (flags == PIPE_TRANSFER_READ) ? PROT_READ : (PROT_READ | PROT_WRITE);
-   kms_sw_dt->mapped = mmap(0, kms_sw_dt->size, prot, MAP_SHARED,
-                            kms_sw->fd, map_req.offset);
-
-   if (kms_sw_dt->mapped == MAP_FAILED)
-      return NULL;
+   void **ptr = (flags == PIPE_TRANSFER_READ) ? &kms_sw_dt->ro_mapped : 
&kms_sw_dt->mapped;
+   if (!*ptr) {
+      void *tmp = mmap(0, kms_sw_dt->size, prot, MAP_SHARED,
+                       kms_sw->fd, map_req.offset);
+      if (tmp == MAP_FAILED)
+         return NULL;
+      *ptr = tmp;
+   }
 
    DEBUG_PRINT("KMS-DEBUG: mapped buffer %u (size %u) at %p\n",
-         kms_sw_dt->handle, kms_sw_dt->size, kms_sw_dt->mapped);
+         kms_sw_dt->handle, kms_sw_dt->size, *ptr);
+
+   kms_sw_dt->map_count++;
 
-   return kms_sw_dt->mapped;
+   return *ptr;
 }
 
 static struct kms_sw_displaytarget *
@@ -277,10 +288,23 @@ kms_sw_displaytarget_unmap(struct sw_winsys *ws,
 {
    struct kms_sw_displaytarget *kms_sw_dt = kms_sw_displaytarget(dt);
 
+   if (!kms_sw_dt->map_count)  {
+      DEBUG_PRINT("KMS-DEBUG: ignore duplicated unmap %u", kms_sw_dt->handle);
+      return;
+   }
+   kms_sw_dt->map_count--;
+   if (kms_sw_dt->map_count) {
+      DEBUG_PRINT("KMS-DEBUG: ignore unmap for busy buffer %u", 
kms_sw_dt->handle);
+      return;
+   }
+
    DEBUG_PRINT("KMS-DEBUG: unmapped buffer %u (was %p)\n", kms_sw_dt->handle, 
kms_sw_dt->mapped);
+   DEBUG_PRINT("KMS-DEBUG: unmapped buffer %u (was %p)\n", kms_sw_dt->handle, 
kms_sw_dt->ro_mapped);
 
    munmap(kms_sw_dt->mapped, kms_sw_dt->size);
    kms_sw_dt->mapped = NULL;
+   munmap(kms_sw_dt->ro_mapped, kms_sw_dt->size);
+   kms_sw_dt->ro_mapped = NULL;
 }
 
 static struct sw_displaytarget *
-- 
2.16.2.804.g6dcf76e118-goog

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