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[Qemu-block] [PATCH v2] util/async: avoid NULL pointer dereference


From: Jie Wang
Subject: [Qemu-block] [PATCH v2] util/async: avoid NULL pointer dereference
Date: Tue, 12 Jun 2018 07:26:25 +0800

if laio_init create linux_aio failed and return NULL, NULL pointer
dereference will occur when laio_attach_aio_context dereference
linux_aio in aio_get_linux_aio. Let's avoid it and report error.

Signed-off-by: Jie Wang <address@hidden>
---
 block/file-posix.c | 19 +++++++++++++++++--
 util/async.c       |  5 ++++-
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c
index 513d371bb1..653017d7a5 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1665,6 +1665,11 @@ static int coroutine_fn raw_co_prw(BlockDriverState *bs, 
uint64_t offset,
 #ifdef CONFIG_LINUX_AIO
         } else if (s->use_linux_aio) {
             LinuxAioState *aio = aio_get_linux_aio(bdrv_get_aio_context(bs));
+            if (!aio) {
+                s->use_linux_aio = false;
+                error_report("Failed to get linux aio");
+                return -EIO;
+            }
             assert(qiov->size == bytes);
             return laio_co_submit(bs, aio, s->fd, offset, qiov, type);
 #endif
@@ -1695,7 +1700,12 @@ static void raw_aio_plug(BlockDriverState *bs)
     BDRVRawState *s = bs->opaque;
     if (s->use_linux_aio) {
         LinuxAioState *aio = aio_get_linux_aio(bdrv_get_aio_context(bs));
-        laio_io_plug(bs, aio);
+        if (aio) {
+            laio_io_plug(bs, aio);
+        } else {
+            s->use_linux_aio = false;
+            error_report("Failed to get linux aio");
+        }
     }
 #endif
 }
@@ -1706,7 +1716,12 @@ static void raw_aio_unplug(BlockDriverState *bs)
     BDRVRawState *s = bs->opaque;
     if (s->use_linux_aio) {
         LinuxAioState *aio = aio_get_linux_aio(bdrv_get_aio_context(bs));
-        laio_io_unplug(bs, aio);
+        if (aio) {
+            laio_io_unplug(bs, aio);
+        } else {
+            s->use_linux_aio = false;
+            error_report("Failed to get linux aio");
+        }
     }
 #endif
 }
diff --git a/util/async.c b/util/async.c
index 03f62787f2..08d71340f8 100644
--- a/util/async.c
+++ b/util/async.c
@@ -327,8 +327,11 @@ LinuxAioState *aio_get_linux_aio(AioContext *ctx)
 {
     if (!ctx->linux_aio) {
         ctx->linux_aio = laio_init();
-        laio_attach_aio_context(ctx->linux_aio, ctx);
+        if (ctx->linux_aio) {
+            laio_attach_aio_context(ctx->linux_aio, ctx);
+        }
     }
+
     return ctx->linux_aio;
 }
 #endif
-- 
2.15.0.windows.1




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