From e95205e1f9cd2c4262b7a7b1c992a94512c86d0e Mon Sep 17 00:00:00 2001 From: Fam Zheng Date: Mon, 16 Mar 2015 17:03:37 +0800 Subject: [PATCH] dma-helpers: Fix race condition of continue_after_map_failure and dma_aio_cancel If DMA's owning thread cancels the IO while the bounce buffer's owning thread is notifying the "cpu client list", a use-after-free happens: continue_after_map_failure dma_aio_cancel ------------------------------------------------------------------ aio_bh_new qemu_bh_delete qemu_bh_schedule (use after free) Also, the old code doesn't run the bh in the right AioContext. Fix both problems by passing a QEMUBH to cpu_register_map_client. Signed-off-by: Fam Zheng Reviewed-by: Paolo Bonzini Message-Id: <1426496617-10702-6-git-send-email-famz@redhat.com> [Remove unnecessary forward declaration. - Paolo] Signed-off-by: Paolo Bonzini --- dma-helpers.c | 17 ++++++++--------- exec.c | 34 +++++++++++++++++++++------------- include/exec/cpu-common.h | 3 ++- 3 files changed, 31 insertions(+), 23 deletions(-) diff --git a/dma-helpers.c b/dma-helpers.c index 6918572e18..1fddf6a11c 100644 --- a/dma-helpers.c +++ b/dma-helpers.c @@ -92,14 +92,6 @@ static void reschedule_dma(void *opaque) dma_blk_cb(dbs, 0); } -static void continue_after_map_failure(void *opaque) -{ - DMAAIOCB *dbs = (DMAAIOCB *)opaque; - - dbs->bh = qemu_bh_new(reschedule_dma, dbs); - qemu_bh_schedule(dbs->bh); -} - static void dma_blk_unmap(DMAAIOCB *dbs) { int i; @@ -161,7 +153,9 @@ static void dma_blk_cb(void *opaque, int ret) if (dbs->iov.size == 0) { trace_dma_map_wait(dbs); - cpu_register_map_client(dbs, continue_after_map_failure); + dbs->bh = aio_bh_new(blk_get_aio_context(dbs->blk), + reschedule_dma, dbs); + cpu_register_map_client(dbs->bh); return; } @@ -183,6 +177,11 @@ static void dma_aio_cancel(BlockAIOCB *acb) if (dbs->acb) { blk_aio_cancel_async(dbs->acb); } + if (dbs->bh) { + cpu_unregister_map_client(dbs->bh); + qemu_bh_delete(dbs->bh); + dbs->bh = NULL; + } } diff --git a/exec.c b/exec.c index 2c87f1d6d6..065f5e8360 100644 --- a/exec.c +++ b/exec.c @@ -2479,8 +2479,7 @@ typedef struct { static BounceBuffer bounce; typedef struct MapClient { - void *opaque; - void (*callback)(void *opaque); + QEMUBH *bh; QLIST_ENTRY(MapClient) link; } MapClient; @@ -2488,31 +2487,34 @@ QemuMutex map_client_list_lock; static QLIST_HEAD(map_client_list, MapClient) map_client_list = QLIST_HEAD_INITIALIZER(map_client_list); -static void cpu_unregister_map_client(void *_client); +static void cpu_unregister_map_client_do(MapClient *client) +{ + QLIST_REMOVE(client, link); + g_free(client); +} + static void cpu_notify_map_clients_locked(void) { MapClient *client; while (!QLIST_EMPTY(&map_client_list)) { client = QLIST_FIRST(&map_client_list); - client->callback(client->opaque); - cpu_unregister_map_client(client); + qemu_bh_schedule(client->bh); + cpu_unregister_map_client_do(client); } } -void *cpu_register_map_client(void *opaque, void (*callback)(void *opaque)) +void cpu_register_map_client(QEMUBH *bh) { MapClient *client = g_malloc(sizeof(*client)); qemu_mutex_lock(&map_client_list_lock); - client->opaque = opaque; - client->callback = callback; + client->bh = bh; QLIST_INSERT_HEAD(&map_client_list, client, link); if (!atomic_read(&bounce.in_use)) { cpu_notify_map_clients_locked(); } qemu_mutex_unlock(&map_client_list_lock); - return client; } void cpu_exec_init_all(void) @@ -2523,12 +2525,18 @@ void cpu_exec_init_all(void) qemu_mutex_init(&map_client_list_lock); } -static void cpu_unregister_map_client(void *_client) +void cpu_unregister_map_client(QEMUBH *bh) { - MapClient *client = (MapClient *)_client; + MapClient *client; - QLIST_REMOVE(client, link); - g_free(client); + qemu_mutex_lock(&map_client_list_lock); + QLIST_FOREACH(client, &map_client_list, link) { + if (client->bh == bh) { + cpu_unregister_map_client_do(client); + break; + } + } + qemu_mutex_unlock(&map_client_list_lock); } static void cpu_notify_map_clients(void) diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h index fcc316271e..43428bd030 100644 --- a/include/exec/cpu-common.h +++ b/include/exec/cpu-common.h @@ -82,7 +82,8 @@ void *cpu_physical_memory_map(hwaddr addr, int is_write); void cpu_physical_memory_unmap(void *buffer, hwaddr len, int is_write, hwaddr access_len); -void *cpu_register_map_client(void *opaque, void (*callback)(void *opaque)); +void cpu_register_map_client(QEMUBH *bh); +void cpu_unregister_map_client(QEMUBH *bh); bool cpu_physical_memory_is_io(hwaddr phys_addr);