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* [newlib-cygwin/main] nano-mallocr: Prevent NULL pointer de-reference in free_list
@ 2023-02-27 9:58 Corinna Vinschen
0 siblings, 0 replies; only message in thread
From: Corinna Vinschen @ 2023-02-27 9:58 UTC (permalink / raw)
To: newlib-cvs
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=c8397ae8171f00dcfb071130e6ea2b64aea17ded
commit c8397ae8171f00dcfb071130e6ea2b64aea17ded
Author: Henrik Nilsson via Newlib <newlib@sourceware.org>
AuthorDate: Fri Feb 17 06:56:49 2023 +0100
Commit: Corinna Vinschen <corinna@vinschen.de>
CommitDate: Mon Feb 27 10:54:26 2023 +0100
nano-mallocr: Prevent NULL pointer de-reference in free_list
The existing code checked if there was a chunk in free_list and
that the tail was not the next chunk.
The check if there is a chunk is not needed since it's already
known but the case of a single chunk in free_list needs to be
handled differently.
Diff:
---
newlib/libc/stdlib/nano-mallocr.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/newlib/libc/stdlib/nano-mallocr.c b/newlib/libc/stdlib/nano-mallocr.c
index b2273ba60943..a2b50facc35e 100644
--- a/newlib/libc/stdlib/nano-mallocr.c
+++ b/newlib/libc/stdlib/nano-mallocr.c
@@ -333,14 +333,23 @@ void * nano_malloc(RARG malloc_size_t s)
{
p->size += alloc_size;
- /* Remove chunk from free_list */
+ /* Remove chunk from free_list. Since p != NULL there is
+ at least one chunk */
r = free_list;
- while (r && p != r->next)
+ if (r->next == NULL)
{
- r = r->next;
+ /* There is only a single chunk, remove it */
+ free_list = NULL;
+ }
+ else
+ {
+ /* Search for the chunk before the one to be removed */
+ while (p != r->next)
+ {
+ r = r->next;
+ }
+ r->next = NULL;
}
- r->next = NULL;
-
r = p;
}
else
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2023-02-27 9:58 [newlib-cygwin/main] nano-mallocr: Prevent NULL pointer de-reference in free_list Corinna Vinschen
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