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 <[email protected]>
Fixes: d891f28df9a ("gallium/winsys/kms: Fix possible leak in map/unmap.")
Cc: Lepton Wu <[email protected]>
Reviewed-by: Emil Velikov <[email protected]>

1 files 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 3fe1b1a7313..9564d9424b1 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 *