On 5/24/2024 12:33 PM, Greg KH wrote:
On Fri, May 24, 2024 at 12:20:03PM +0800, Zijun Hu wrote:
zap_modalias_env() wrongly calculates size of memory block to move, so maybe cause OOB memory access issue, fixed by correcting size to memmove.
"maybe" or "does"? That's a big difference :)
i found this issue by reading code instead of really meeting this issue. this issue should be prone to happen if there are more than 1 other environment vars.
do you have suggestion about term to use?
Fixes: 9b3fa47d4a76 ("kobject: fix suppressing modalias in uevents delivered over netlink") Cc: stable@vger.kernel.org Signed-off-by: Zijun Hu quic_zijuhu@quicinc.com
lib/kobject_uevent.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 03b427e2707e..f153b4f9d4d9 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -434,7 +434,7 @@ static void zap_modalias_env(struct kobj_uevent_env *env) if (i != env->envp_idx - 1) { memmove(env->envp[i], env->envp[i + 1],
env->buflen - len);
env->buf + env->buflen - env->envp[i + 1]);How is this "more correct"? Please explain it better, this logic is not obvious at all.
env->envp[] contains pointers to env->buf[] with length env->buflen, we want to delete environment variable pointed by env->envp[i] with length @len as shown below.
env->buf[] |-> target block <-| 0-----------------------------------------env->buflen ^ ^ | -> @len <- | env->envp[i] env->envp[i+1]
so move "target block" forward by @len, so size of target block is env->buf + env->buflen - env->envp[i+1] instead of env->buflen -len.
do you suggest add inline comments to explain it ?
thanks,
greg k-h