Mesa (18.2): gallium/winsys/kms: don't unmap what wasn't mapped

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Module: Mesa
Branch: 18.2
Commit: 43208511981aff918fc779f66708818aef9eca81
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=43208511981aff918fc779f66708818aef9eca81

Author: Ray Strode <rstrode at redhat.com>
Date:   Thu Aug 16 16:37:25 2018 -0400

gallium/winsys/kms: don't unmap what wasn't mapped

At the moment, depending on pipe transfer flags, the dumb
buffer map address can end up at either kms_sw_dt->ro_mapped
or kms_sw_dt->mapped.

When it's time to unmap the dumb buffer, both locations get unmapped,
even though one is probably initialized to 0.

That leads to the code segment getting unmapped at runtime and
crashes when trying to call into unrelated code.

This commit addresses the problem by using MAP_FAILED instead of
NULL for ro_mapped and mapped when the dumb buffer is unmapped,
and only unmapping mapped addresses at unmap time.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107098
Signed-off-by: Ray Strode <rstrode at redhat.com>
Fixes: d891f28df9a ("gallium/winsys/kms: Fix possible leak in map/unmap.")
Cc: Lepton Wu <lepton at chromium.org>
Reviewed-by: Emil Velikov <emil.velikov at collabora.com>
(cherry picked from commit 9baff597ce021f7691187b0d1d1bbc16d07b13e1)

---

 src/gallium/winsys/sw/kms-dri/kms_dri_sw_winsys.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 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 3fe1b1a731..9564d9424b 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
@@ -176,6 +176,8 @@ kms_sw_displaytarget_create(struct sw_winsys *ws,
 
    list_inithead(&kms_sw_dt->planes);
    kms_sw_dt->ref_count = 1;
+   kms_sw_dt->mapped = MAP_FAILED;
+   kms_sw_dt->ro_mapped = MAP_FAILED;
 
    kms_sw_dt->format = format;
 
@@ -262,7 +264,7 @@ kms_sw_displaytarget_map(struct sw_winsys *ws,
 
    prot = (flags == PIPE_TRANSFER_READ) ? PROT_READ : (PROT_READ | PROT_WRITE);
    void **ptr = (flags == PIPE_TRANSFER_READ) ? &kms_sw_dt->ro_mapped : &kms_sw_dt->mapped;
-   if (!*ptr) {
+   if (*ptr == MAP_FAILED) {
       void *tmp = mmap(0, kms_sw_dt->size, prot, MAP_SHARED,
                        kms_sw->fd, map_req.offset);
       if (tmp == MAP_FAILED)
@@ -332,6 +334,8 @@ kms_sw_displaytarget_add_from_prime(struct kms_sw_winsys *kms_sw, int fd,
       FREE(kms_sw_dt);
       return NULL;
    }
+   kms_sw_dt->mapped = MAP_FAILED;
+   kms_sw_dt->ro_mapped = MAP_FAILED;
    kms_sw_dt->size = lseek_ret;
    kms_sw_dt->ref_count = 1;
    kms_sw_dt->handle = handle;
@@ -368,10 +372,14 @@ kms_sw_displaytarget_unmap(struct sw_winsys *ws,
    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;
+   if (kms_sw_dt->mapped != MAP_FAILED) {
+      munmap(kms_sw_dt->mapped, kms_sw_dt->size);
+      kms_sw_dt->mapped = MAP_FAILED;
+   }
+   if (kms_sw_dt->ro_mapped != MAP_FAILED) {
+      munmap(kms_sw_dt->ro_mapped, kms_sw_dt->size);
+      kms_sw_dt->ro_mapped = MAP_FAILED;
+   }
 }
 
 static struct sw_displaytarget *