Description
In the Linux kernel, the following vulnerability has been resolved: drm/drm_file: Fix pid refcounting race , Maxime Ripard , Thomas Zimmermann filp->pid is supposed to be a refcounted pointer; however, before this patch, drm_file_update_pid() only increments the refcount of a struct pid after storing a pointer to it in filp->pid and dropping the dev->filelist_mutex, making the following race possible: process A process B ========= ========= begin drm_file_update_pid mutex_lock(&dev->filelist_mutex) rcu_replace_pointer(filp->pid, , 1) mutex_unlock(&dev->filelist_mutex) begin drm_file_update_pid mutex_lock(&dev->filelist_mutex) rcu_replace_pointer(filp->pid, , 1) mutex_unlock(&dev->filelist_mutex) get_pid() synchronize_rcu() put_pid() *** pid B reaches refcount 0 and is freed here *** get_pid() *** UAF *** synchronize_rcu() put_pid() As far as I know, this race can only occur with CONFIG_PREEMPT_RCU=y because it requires RCU to detect a quiescent state in code that is not explicitly calling into the scheduler. This race leads to use-after-free of a "struct pid". It is probably somewhat hard to hit because process A has to pass through a synchronize_rcu() operation while process B is between mutex_unlock() and get_pid(). Fix it by ensuring that by the time a pointer to the current task's pid is stored in the file, an extra reference to the pid has been taken. This fix also removes the condition for synchronize_rcu(); I think that optimization is unnecessary complexity, since in that case we would usually have bailed out on the lockless check above.
Details
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Affected Packages
| Software | From version | Fixed in |
|---|---|---|
| linux | — | 6.8.0-48.48 |
| linux-allwinner-5.19 | — | — |
| linux-aws | — | 6.8.0-1018.20 |
| linux-aws-5.0 | — | — |
| linux-aws-5.11 | — | — |
| linux-aws-5.13 | — | — |
| linux-aws-5.19 | — | — |
| linux-aws-5.3 | — | — |
| linux-aws-5.8 | — | — |
| linux-aws-6.2 | — | — |
| linux-aws-6.5 | — | — |
| linux-aws-6.8 | — | 6.8.0-1018.19~22.04.1 |
| linux-azure | — | 6.8.0-1017.20 |
| linux-azure-5.11 | — | — |
| linux-azure-5.13 | — | — |
| linux-azure-5.19 | — | — |
| linux-azure-5.3 | — | — |
| linux-azure-5.8 | — | — |
| linux-azure-6.2 | — | — |
| linux-azure-6.5 | — | — |
| linux-azure-6.8 | — | 6.8.0-1017.20~22.04.1 |
| linux-azure-edge | — | — |
| linux-azure-fde | — | — |
| linux-azure-fde-5.19 | — | — |
| linux-azure-fde-6.2 | — | — |
| linux-gcp | — | 6.8.0-1017.19 |
| linux-gcp-5.11 | — | — |
| linux-gcp-5.13 | — | — |
| linux-gcp-5.19 | — | — |
| linux-gcp-5.3 | — | — |
| linux-gcp-5.8 | — | — |
| linux-gcp-6.2 | — | — |
| linux-gcp-6.5 | — | — |
| linux-gcp-6.8 | — | 6.8.0-1017.19~22.04.1 |
| linux-gke | — | 6.8.0-1013.17 |
| linux-gke-4.15 | — | — |
| linux-gke-5.15 | — | — |
| linux-gke-5.4 | — | — |
| linux-gkeop | — | 6.8.0-1002.4 |
| linux-gkeop-5.4 | — | — |
| linux-hwe | — | — |
| linux-hwe-5.11 | — | — |
| linux-hwe-5.13 | — | — |
| linux-hwe-5.19 | — | — |
| linux-hwe-5.8 | — | — |
| linux-hwe-6.2 | — | — |
| linux-hwe-6.5 | — | — |
| linux-hwe-6.8 | — | 6.8.0-48.48~22.04.1 |
| linux-hwe-edge | — | — |
| linux-ibm | — | 6.8.0-1015.15 |
| linux-intel-5.13 | — | — |
| linux-intel-iot-realtime | — | — |
| linux-lowlatency | — | 6.8.0-48.48.3 |
| linux-lowlatency-hwe-5.19 | — | — |
| linux-lowlatency-hwe-6.2 | — | — |
| linux-lowlatency-hwe-6.5 | — | — |
| linux-lowlatency-hwe-6.8 | — | 6.8.0-48.48.3~22.04.1 |
| linux-nvidia | — | 6.8.0-1017.19 |
| linux-nvidia-6.2 | — | — |
| linux-nvidia-6.5 | — | — |
| linux-nvidia-6.8 | — | 6.8.0-1017.19~22.04.1 |
| linux-nvidia-lowlatency | — | 6.8.0-1017.19.1 |
| linux-oem | — | — |
| linux-oem-5.10 | — | — |
| linux-oem-5.13 | — | — |
| linux-oem-5.14 | — | — |
| linux-oem-5.17 | — | — |
| linux-oem-5.6 | — | — |
| linux-oem-6.0 | — | — |
| linux-oem-6.1 | — | — |
| linux-oem-6.5 | — | — |
| linux-oem-6.8 | — | 6.8.0-1016.16 |
| linux-oracle | — | 6.8.0-1015.16 |
| linux-oracle-5.0 | — | — |
| linux-oracle-5.11 | — | — |
| linux-oracle-5.13 | — | — |
| linux-oracle-5.3 | — | — |
| linux-oracle-5.8 | — | — |
| linux-oracle-6.5 | — | — |
| linux-oracle-6.8 | — | 6.8.0-1015.15~22.04.1 |
| linux-raspi | — | 6.8.0-1014.16 |
| linux-raspi-realtime | — | 6.8.0-2013.14 |
| linux-raspi2 | — | — |
| linux-realtime | — | 6.8.1-1011.11 |
| linux-riscv | — | 6.8.0-48.48.1 |
| linux-riscv-5.11 | — | — |
| linux-riscv-5.19 | — | — |
| linux-riscv-5.8 | — | — |
| linux-riscv-6.5 | — | — |
| linux-riscv-6.8 | — | 6.8.0-48.48.1~22.04.2 |
| linux-starfive-5.19 | — | — |
| linux-starfive-6.2 | — | — |
| linux-starfive-6.5 | — | — |
References
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