From: Henrik Nilsson <henrik.nilsson@bytequest.se>
To: newlib@sourceware.org
Cc: Henrik Nilsson <henrik.nilsson@bytequest.se>
Subject: [PATCH] nano-mallocr: Prevent NULL pointer de-reference in free_list
Date: Fri, 17 Feb 2023 06:56:49 +0100 [thread overview]
Message-ID: <20230217055649.3591878-1-henrik.nilsson@bytequest.se> (raw)
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.
---
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 b2273ba60..a2b50facc 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
--
2.34.1
next reply other threads:[~2023-02-17 5:57 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-17 5:56 Henrik Nilsson [this message]
2023-02-23 6:59 ` Henrik Nilsson
2023-02-27 10:00 ` Corinna Vinschen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230217055649.3591878-1-henrik.nilsson@bytequest.se \
--to=henrik.nilsson@bytequest.se \
--cc=newlib@sourceware.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).