The patch titled
Subject: bootconfig: fix off-by-one in xbc_node_compose_key_after()
has been added to the -mm tree. Its filename is
bootconfig-fix-off-by-one-in-xbc_node_compose_key_after.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/bootconfig-fix-off-by-one-in-xbc_node_compose_key_after.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/bootconfig-fix-off-by-one-in-xbc_node_compose_key_after.patch
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------------------------------------------------------
From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Subject: bootconfig: fix off-by-one in xbc_node_compose_key_after()
While reviewing some patches for bootconfig, I noticed the following
code in xbc_node_compose_key_after():
ret = snprintf(buf, size, "%s%s", xbc_node_get_data(node),
depth ? "." : "");
if (ret < 0)
return ret;
if (ret > size) {
size = 0;
} else {
size -= ret;
buf += ret;
}
But snprintf() returns the number of bytes that would be written, not
the number of bytes that are written (ignoring the nul terminator).
This means that if the number of non null bytes written were to equal
size, then the nul byte, which snprintf() always adds, will overwrite
that last byte.
ret = snprintf(buf, 5, "hello");
printf("buf = '%s'
", buf);
printf("ret = %d
", ret);
produces:
buf = 'hell'
ret = 5
The string was truncated without ret being greater than 5.
Test (ret >= size) for overwrite.
Link: http://lkml.kernel.org/r/20200813183050.029a6003@xxxxxxxxxxxxxxxx
Fixes: 76db5a27a827c ("bootconfig: Add Extra Boot Config support")
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/bootconfig.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/lib/bootconfig.c~bootconfig-fix-off-by-one-in-xbc_node_compose_key_after
+++ a/lib/bootconfig.c
@@ -248,7 +248,7 @@ int __init xbc_node_compose_key_after(st
depth ? "." : "");
if (ret < 0)
return ret;
- if (ret > size) {
+ if (ret >= size) {
size = 0;
} else {
size -= ret;
_
Patches currently in -mm which might be from rostedt@xxxxxxxxxxx are
bootconfig-fix-off-by-one-in-xbc_node_compose_key_after.patch
