OP-TEE January 2023

op-tee@lists.trustedfirmware.org

13 participants
11 discussions

[PATCH] tee: optee: smc_abi: Fix use-after-free in optee_smc_open

by Yoochan Lee

A race condition may occur if the user physically removes the smc_abi device while calling open(). This is a race condition between optee_smc_open() function and the optee_smc_remove() function, which may lead to Use-After-Free. Therefore, add a refcount check to optee_smc_remove() function to free the "optee" structure after the device is close()d. ---------------CPU 0--------------------CPU 1----------------- optee_smc_open() | optee_smc_remove() -------------------------------------------------------------- struct optee *optee = tee_get_| drvdata(ctx->teedev); — (1) | | struct optee *optee = platform_ | get_drvdata(pdev); | ... | kfree(optee); — (2) u32 sec_caps = optee->smc.sec_| caps; — (3) Signed-off-by: Yoochan Lee <yoochan1026(a)gmail.com> --- drivers/tee/optee/optee_private.h | 1 + drivers/tee/optee/smc_abi.c | 66 ++++++++++++++++++++++--------- 2 files changed, 48 insertions(+), 19 deletions(-) diff --git a/drivers/tee/optee/optee_private.h b/drivers/tee/optee/optee_private.h index 04ae58892608..f52b1cf20eab 100644 --- a/drivers/tee/optee/optee_private.h +++ b/drivers/tee/optee/optee_private.h @@ -175,6 +175,7 @@ struct optee { bool scan_bus_done; struct workqueue_struct *scan_bus_wq; struct work_struct scan_bus_work; + struct kref refcnt; }; struct optee_session { diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c index a1c1fa1a9c28..4fbec2acc255 100644 --- a/drivers/tee/optee/smc_abi.c +++ b/drivers/tee/optee/smc_abi.c @@ -1077,18 +1077,61 @@ static void optee_get_version(struct tee_device *teedev, *vers = v; } +static void optee_smc_delete(struct kref *kref) +{ + struct optee *optee = container_of(kref, struct optee, refcnt); + + /* + * Ask OP-TEE to free all cached shared memory objects to decrease + * reference counters and also avoid wild pointers in secure world + * into the old shared memory range. + */ + if (!optee->rpc_param_count) + optee_disable_shm_cache(optee); + + optee_smc_notif_uninit_irq(optee); + + optee_remove_common(optee); + + if (optee->smc.memremaped_shm) + memunmap(optee->smc.memremaped_shm); + + kfree(optee); +} + +static void optee_smc_release_supp(struct tee_context *ctx) +{ + struct optee *optee = tee_get_drvdata(ctx->teedev); + + optee_release_helper(ctx, optee_close_session_helper); + if (optee->scan_bus_wq) { + destroy_workqueue(optee->scan_bus_wq); + optee->scan_bus_wq = NULL; + } + optee_supp_release(&optee->supp); + kref_put(&optee->refcnt, optee_smc_delete); +} + +static void optee_smc_release(struct tee_context *ctx) +{ + struct optee *optee = tee_get_drvdata(ctx->teedev); + + optee_release_helper(ctx, optee_close_session_helper); + kref_put(&optee->refcnt, optee_smc_delete); +} + static int optee_smc_open(struct tee_context *ctx) { struct optee *optee = tee_get_drvdata(ctx->teedev); u32 sec_caps = optee->smc.sec_caps; - + kref_get(&optee->refcnt); return optee_open(ctx, sec_caps & OPTEE_SMC_SEC_CAP_MEMREF_NULL); } static const struct tee_driver_ops optee_clnt_ops = { .get_version = optee_get_version, .open = optee_smc_open, - .release = optee_release, + .release = optee_smc_release, .open_session = optee_open_session, .close_session = optee_close_session, .invoke_func = optee_invoke_func, @@ -1106,7 +1149,7 @@ static const struct tee_desc optee_clnt_desc = { static const struct tee_driver_ops optee_supp_ops = { .get_version = optee_get_version, .open = optee_smc_open, - .release = optee_release_supp, + .release = optee_smc_release_supp, .supp_recv = optee_supp_recv, .supp_send = optee_supp_send, .shm_register = optee_shm_register_supp, @@ -1319,22 +1362,7 @@ static int optee_smc_remove(struct platform_device *pdev) { struct optee *optee = platform_get_drvdata(pdev); - /* - * Ask OP-TEE to free all cached shared memory objects to decrease - * reference counters and also avoid wild pointers in secure world - * into the old shared memory range. - */ - if (!optee->rpc_param_count) - optee_disable_shm_cache(optee); - - optee_smc_notif_uninit_irq(optee); - - optee_remove_common(optee); - - if (optee->smc.memremaped_shm) - memunmap(optee->smc.memremaped_shm); - - kfree(optee); + kref_put(&optee->refcnt, optee_smc_delete); return 0; } -- 2.39.0

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