On 5/29/2024 2:56 AM, Dmitry Torokhov wrote:
On Tue, May 28, 2024 at 11:19:07AM +0800, Zijun Hu wrote:
zap_modalias_env() wrongly calculates size of memory block to move, so will cause OOB memory access issue if variable MODALIAS is not the last one within its @env parameter, fixed by correcting size to memmove.
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
V1 -> V2: Correct commit messages and add inline comments
V1 discussion link: https://lore.kernel.org/lkml/0b916393-eb39-4467-9c99-ac1bc9746512@quicinc.co...
lib/kobject_uevent.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index 03b427e2707e..f22366be020c 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -433,8 +433,23 @@ static void zap_modalias_env(struct kobj_uevent_env *env) len = strlen(env->envp[i]) + 1; if (i != env->envp_idx - 1) {
/* @env->envp[] contains pointers to @env->buf[]* with @env->buflen elements, and we want to* remove variable MODALIAS pointed by* @env->envp[i] with length @len as shown below:** 0 @env->buf[] @env->buflen* ----------------------------------------* ^ ^ ^* |-> @len <-| target block |* @env->envp[i] @env->envp[i+1]** so the "target block" indicated above is moved* backward by @len, and its right size is* (@env->buf + @env->buflen - @env->envp[i + 1]).*/ memmove(env->envp[i], env->envp[i + 1],
env->buflen - len);
env->buf + env->buflen - env->envp[i + 1]);Thank you for noticing this, it is indeed a bug.
I wonder if this would not be expressed better as:
tail_len = env->buflen - (env->envp[i + 1] - env->envp[0]); memmove(env->envp[i], env->envp[i + 1], tail_len);and we would not need the large comment.
Greg KH suggests add inline comments since my fix is not obvious with first glance, let us wait for his comments within 2 days about below question: is it okay to remove those inline comments if block size to move is changed to env->buflen - (env->envp[i + 1] - env->envp[0]) ?
Otherwise:
Acked-by: Dmitry Torokhov dmitry.torokhov@gmail.com
for (j = i; j < env->envp_idx - 1; j++) env->envp[j] = env->envp[j + 1] - len; -- 2.7.4
Thanks.