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sysfsutils: fix my_strncat function

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The bug was introduced by upstream commit [1] where strncat was replaced with
internal my_strncat function, such as:

  char dest[32] = "/sys/devices/platform/axi";
  my_strncat(dest, "/", sizeof(dest) - strlen(dest) - 1);

Will result in dest string being:

  /sys/

and not the expected:

  /sys/devices/platform/axi/

The meaning of the "len" parameter in the my_strncat function is the size limit for
copying characters from "from", not the size limit for "to" after copying. Also,
the "#define safestrcat(to, from) my_strncat(to, from, sizeof(to) - strlen(to) - 1)"
has already imposed a limit on max based on the size of "to". Modify the function
to prevent truncation of content when too many bytes are passed to the my_strcat function.

[1] 0719881cad

(From OE-Core rev: a5d2a5ce94b82957e2a9336c18dce9b28073cd71)

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
This commit is contained in:
Hongxu Jia
2025-06-04 16:17:44 +08:00
committed by Richard Purdie
parent 72d932cc5b
commit 2922e9cebf
2 changed files with 37 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

34
meta/recipes-core/sysfsutils/files/0001-Modify-my_strncat-function.patch Normal file
View File

@@ -0,0 +1,34 @@
From a13fc5a57ea7c6b1761bc204cb79d8ce4745f57a Mon Sep 17 00:00:00 2001
From: songliang <YS.songliang@h3c.com>
Date: Wed, 4 Jun 2025 15:58:53 +0800
Subject: [PATCH] Modify "my_strncat" function
The meaning of the "len" parameter in the my_strncat function is the size limit for copying characters from "from", not the size limit for "to" after copying.
Also, the "#define safestrcat(to, from) my_strncat(to, from, sizeof(to) - strlen(to) - 1)" has already imposed a limit on max based on the size of "to".
Modify the function to prevent truncation of content when too many bytes are passed to the my_strcat function.
Upstream-Status: Submitted [https://github.com/linux-ras/sysfsutils/pull/30/commits/c2326946c0c2a4206c9b079a9fe25f7f9115295c]
Signed-off-by: songliang <YS.songliang@h3c.com>
Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
---
lib/sysfs_utils.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/lib/sysfs_utils.c b/lib/sysfs_utils.c
index 46e0849..c0176d1 100644
--- a/lib/sysfs_utils.c
+++ b/lib/sysfs_utils.c
@@ -375,8 +375,8 @@ char *my_strncat(char *to, const char *from, size_t max)
{
size_t i = 0;
- while (i < max && to[i] != '\0')
+ while (to[i] != '\0')
i++;
- my_strncpy(to+i, from, max-i);
+ my_strncpy(to+i, from, max);
return to;
}
--
2.34.1