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_no... and later at http://ozlabs.org/~akpm/mmotm/broken-out/bootconfig-fix-off-by-one-in-xbc_no...
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------------------------------------------------------ From: Steven Rostedt (VMware) rostedt@goodmis.org 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@oasis.local.home Fixes: 76db5a27a827c ("bootconfig: Add Extra Boot Config support") Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Cc: Masami Hiramatsu mhiramat@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
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@goodmis.org are
bootconfig-fix-off-by-one-in-xbc_node_compose_key_after.patch