On 2024/5/30 21:14, 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

---

V3: Correct inline comments and take Dmitry's suggestion V2: Correct commit messages and add inline comments

Previous discussion links: https://lore.kernel.org/lkml/ZlYo20ztfLWPyy5d@google.com/ 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..b7f2fa08d9c8 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 chars, and we are removing
  

• 	 * variable MODALIAS here pointed by @env->envp[i]
  

• 	 * with length @len as shown below:
  

• 	 *
  

• 	 * 0               @env->buf[]      @env->buflen
  

• 	 * ---------------------------------------------
  

• 	 * ^             ^              ^              ^
  

• 	 * |             |->   @len   <-| target block |
  

• 	 * @env->envp[0] @env->envp[i]  @env->envp[i + 1]
  

• 	 *
  

• 	 * so the "target block" indicated above is moved
  

• 	 * backward by @len, and its right size is
  

• 	 * @env->buflen - (@env->envp[i + 1] - @env->envp[0]).
  

• 	 */
  memmove(env->envp[i], env->envp[i + 1],
  

• 		env->buflen - len);
  

• 		env->buflen - (env->envp[i + 1] - env->envp[0]));
  

for (j = i; j < env->envp_idx - 1; j++) env->envp[j] = env->envp[j + 1] - len;

Reviewed-by: Lk Sii lk_sii@163.com