linux 5.10.5: backporting linux upstream patch for 5.10.5 (libsubcmd …

…fix use after free for realloc)

Permits building on top of debian-12 (testing), which fails to build since detecting bug.

patches/linux-5.10.5/0004-libsubcmd_Fix_use-after-free-for-realloc.patch

@@ -0,0 +1,64 @@
+From 52a9dab6d892763b2a8334a568bd4e2c1a6fde66 Mon Sep 17 00:00:00 2001
+From: Kees Cook <[email protected]>
+Date: Sun, 13 Feb 2022 10:24:43 -0800
+Subject: [PATCH] libsubcmd: Fix use-after-free for realloc(..., 0)
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+GCC 12 correctly reports a potential use-after-free condition in the
+xrealloc helper. Fix the warning by avoiding an implicit "free(ptr)"
+when size == 0:
+
+In file included from help.c:12:
+In function 'xrealloc',
+    inlined from 'add_cmdname' at help.c:24:2: subcmd-util.h:56:23: error: pointer may be used after 'realloc' [-Werror=use-after-free]
+   56 |                 ret = realloc(ptr, size);
+      |                       ^~~~~~~~~~~~~~~~~~
+subcmd-util.h:52:21: note: call to 'realloc' here
+   52 |         void *ret = realloc(ptr, size);
+      |                     ^~~~~~~~~~~~~~~~~~
+subcmd-util.h:58:31: error: pointer may be used after 'realloc' [-Werror=use-after-free]
+   58 |                         ret = realloc(ptr, 1);
+      |                               ^~~~~~~~~~~~~~~
+subcmd-util.h:52:21: note: call to 'realloc' here
+   52 |         void *ret = realloc(ptr, size);
+      |                     ^~~~~~~~~~~~~~~~~~
+
+Fixes: 2f4ce5ec1d447beb ("perf tools: Finalize subcmd independence")
+Reported-by: Valdis Klētnieks <[email protected]>
+Signed-off-by: Kees Kook <[email protected]>
+Tested-by: Valdis Klētnieks <[email protected]>
+Tested-by: Justin M. Forbes <[email protected]>
+Acked-by: Josh Poimboeuf <[email protected]>
+Cc: [email protected]
+Cc: Valdis Klētnieks <[email protected]>
+Link: http://lore.kernel.org/lkml/[email protected]
+Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
+---
+ tools/lib/subcmd/subcmd-util.h | 11 ++---------
+ 1 file changed, 2 insertions(+), 9 deletions(-)
+
+diff --git a/tools/lib/subcmd/subcmd-util.h b/tools/lib/subcmd/subcmd-util.h
+index 794a375dad3601..b2aec04fce8f67 100644
+--- a/tools/lib/subcmd/subcmd-util.h
++++ b/tools/lib/subcmd/subcmd-util.h
+@@ -50,15 +50,8 @@ static NORETURN inline void die(const char *err, ...)
+ static inline void *xrealloc(void *ptr, size_t size)
+ {
+ 	void *ret = realloc(ptr, size);
+-	if (!ret && !size)
+-		ret = realloc(ptr, 1);
+-	if (!ret) {
+-		ret = realloc(ptr, size);
+-		if (!ret && !size)
+-			ret = realloc(ptr, 1);
+-		if (!ret)
+-			die("Out of memory, realloc failed");
+-	}
++	if (!ret)
++		die("Out of memory, realloc failed");
+ 	return ret;
+ }
+
+