Re: Fix interval_tree_iter_first() to check root node value

[Richard Henderson]

On 8/9/23 08:11, Helge Deller wrote:
Fix a crash in qemu-user when running
     cat /proc/self/maps

in a chroot, where /proc isn't mounted.

The problem was introduced by commit 3ce3dd8ca965 ("util/selfmap:
Rewrite using qemu/interval-tree.h") where in open_self_maps_1() the
function read_self_maps() is called and which returns NULL if it can't
read the hosts /proc/self/maps file. Afterwards that NULL is fed into
interval_tree_iter_first() which doesn't check if the root node is NULL.

Fix it by adding a check if root is NULL and return NULL in that case.

Signed-off-by: Helge Deller <del...@gmx.de>
Fixes: 3ce3dd8ca965 ("util/selfmap: Rewrite using qemu/interval-tree.h")

diff --git a/util/interval-tree.c b/util/interval-tree.c
index f2866aa7d3..53465182e6 100644
--- a/util/interval-tree.c
+++ b/util/interval-tree.c
@@ -797,7 +797,7 @@ IntervalTreeNode *interval_tree_iter_first(IntervalTreeRoot 
*root,
  {
      IntervalTreeNode *node, *leftmost;

-    if (!root->rb_root.rb_node) {
+    if (!root || !root->rb_root.rb_node) {


I guess this is good enough for 8.1.  Before the conversion to interval-tree we would also 
emit nothing.

I've already done a rewrite for 8.2, and I noticed this problem.  There I emit what 
mapping information that I have, which is everything except for the device+path data.

Reviewed-by: Richard Henderson <richard.hender...@linaro.org>


r~