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[66.131.184.68]) by smtp.gmail.com with ESMTPSA id b24sm2578996qtt.44.2021.02.17.19.21.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 17 Feb 2021 19:21:56 -0800 (PST) From: Jonathan Marek To: linux-arm-msm@vger.kernel.org Cc: srinivas.kandagatla@linaro.org, Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org (open list) Subject: [PATCH 2/3] fastrpc: move fl->maps list removal into fastrpc_free_map Date: Wed, 17 Feb 2021 22:20:54 -0500 Message-Id: <20210218032055.28247-3-jonathan@marek.ca> X-Mailer: git-send-email 2.26.1 In-Reply-To: <20210218032055.28247-1-jonathan@marek.ca> References: <20210218032055.28247-1-jonathan@marek.ca> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org This fixes the incredibly broken behavior of fastrpc_context_free(), which calls fastrpc_map_put() but does not remove the map from the list when it is free'd, causing use-after-free errors. fl->lock needs to be held not just for list_del(), but also kref_put, to avoid a race condition with fastrpc_map_find() logic. Signed-off-by: Jonathan Marek --- drivers/misc/fastrpc.c | 27 +++++++++++++-------------- 1 file changed, 13 insertions(+), 14 deletions(-) diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c index 4fabea0c1551..170352b43ab6 100644 --- a/drivers/misc/fastrpc.c +++ b/drivers/misc/fastrpc.c @@ -245,19 +245,21 @@ static void fastrpc_free_map(struct kref *ref) dma_buf_put(map->buf); } + list_del(&map->node); + kfree(map); } static void fastrpc_map_put(struct fastrpc_map *map) { - if (map) - kref_put(&map->refcount, fastrpc_free_map); + spin_lock(&map->fl->lock); + kref_put(&map->refcount, fastrpc_free_map); + spin_unlock(&map->fl->lock); } static void fastrpc_map_get(struct fastrpc_map *map) { - if (map) - kref_get(&map->refcount); + kref_get(&map->refcount); } static int fastrpc_map_find(struct fastrpc_user *fl, int fd, @@ -351,8 +353,10 @@ static void fastrpc_context_free(struct kref *ref) ctx = container_of(ref, struct fastrpc_invoke_ctx, refcount); cctx = ctx->cctx; - for (i = 0; i < ctx->nscalars; i++) - fastrpc_map_put(ctx->maps[i]); + for (i = 0; i < ctx->nscalars; i++) { + if (ctx->maps[i]) + fastrpc_map_put(ctx->maps[i]); + } if (ctx->buf) fastrpc_buf_free(ctx->buf); @@ -1103,12 +1107,8 @@ static int fastrpc_init_create_process(struct fastrpc_user *fl, fl->init_mem = NULL; fastrpc_buf_free(imem); err_alloc: - if (map) { - spin_lock(&fl->lock); - list_del(&map->node); - spin_unlock(&fl->lock); + if (map) fastrpc_map_put(map); - } err: kfree(args); @@ -1185,10 +1185,9 @@ static int fastrpc_device_release(struct inode *inode, struct file *file) fastrpc_context_put(ctx); } - list_for_each_entry_safe(map, m, &fl->maps, node) { - list_del(&map->node); + list_for_each_entry_safe(map, m, &fl->maps, node) fastrpc_map_put(map); - } + WARN_ON(!list_empty(&fl->maps)); list_for_each_entry_safe(buf, b, &fl->mmaps, node) { list_del(&buf->node);