patch 9.0.2143: [security]: buffer-overflow in ex_substitute
Problem: [security]: buffer-overflow in ex_substitute
Solution: clear memory after allocating
When allocating the new_start pointer in ex_substitute() the memory
pointer points to some garbage that the following for loop in
ex_cmds.c:4743 confuses and causes it to accessing the new_start pointer
beyond it's size, leading to a buffer-overlow.
So fix this by using alloc_clear() instead of alloc(), which will
clear the memory by NUL and therefore cause the loop to terminate
correctly.
Reported by @henices, thanks!
closes: #13596
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index a08682b..e311fa8 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -4650,7 +4650,7 @@
* too many calls to alloc()/free()).
*/
new_start_len = needed_len + 50;
- if ((new_start = alloc(new_start_len)) == NULL)
+ if ((new_start = alloc_clear(new_start_len)) == NULL)
goto outofmem;
*new_start = NUL;
new_end = new_start;
@@ -4667,7 +4667,7 @@
if (needed_len > (int)new_start_len)
{
new_start_len = needed_len + 50;
- if ((p1 = alloc(new_start_len)) == NULL)
+ if ((p1 = alloc_clear(new_start_len)) == NULL)
{
vim_free(new_start);
goto outofmem;