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authorEric Blake <eblake@redhat.com>2016-04-21 08:42:30 -0600
committerPeter Maydell <peter.maydell@linaro.org>2016-04-22 11:55:35 +0100
commitdf7b97ff89319ccf392a16748081482a3d22b35a (patch)
tree39fa13b93ee515257d1115af97ab5678ed065fd8
parent8d0d9b9f67d6bdee9eaec1e8c1222ad91dc4ac01 (diff)
downloadqemu-arm-df7b97ff89319ccf392a16748081482a3d22b35a.tar.gz
nbd: Don't mishandle unaligned client requests
The NBD protocol does not (yet) force any alignment constraints on clients. Even though qemu NBD clients always send requests that are aligned to 512 bytes, we must be prepared for non-qemu clients that don't care about alignment (even if it means they are less efficient). Our use of blk_read() and blk_write() was silently operating on the wrong file offsets when the client made an unaligned request, corrupting the client's data (but as the client already has control over the file we are serving, I don't think it is a security hole, per se, just a data corruption bug). Note that in the case of NBD_CMD_READ, an unaligned length could cause us to return up to 511 bytes of uninitialized trailing garbage from blk_try_blockalign() - hopefully nothing sensitive from the heap's prior usage is ever leaked in that manner. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Fam Zheng <famz@redhat.com> Tested-by: Kevin Wolf <kwolf@redhat.com> Message-id: 1461249750-31928-1-git-send-email-eblake@redhat.com Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
-rw-r--r--nbd/server.c10
1 files changed, 4 insertions, 6 deletions
diff --git a/nbd/server.c b/nbd/server.c
index a13a69169a..2184c64fef 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -1091,9 +1091,8 @@ static void nbd_trip(void *opaque)
}
}
- ret = blk_read(exp->blk,
- (request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
- req->data, request.len / BDRV_SECTOR_SIZE);
+ ret = blk_pread(exp->blk, request.from + exp->dev_offset,
+ req->data, request.len);
if (ret < 0) {
LOG("reading from file failed");
reply.error = -ret;
@@ -1115,9 +1114,8 @@ static void nbd_trip(void *opaque)
TRACE("Writing to device");
- ret = blk_write(exp->blk,
- (request.from + exp->dev_offset) / BDRV_SECTOR_SIZE,
- req->data, request.len / BDRV_SECTOR_SIZE);
+ ret = blk_pwrite(exp->blk, request.from + exp->dev_offset,
+ req->data, request.len);
if (ret < 0) {
LOG("writing to file failed");
reply.error = -ret;