librbd: readv/writev fix iovecs length computation overflow

iovec have unsigned length (size_t) and before this patch the
total length was computed by adding iovec's length to a signed
length variable (ssize_t). While the code checked if the resulting
length was negative on overflow, the case where length is positive
after overflow was not checked. This patch fixes the overflow check
by changing length to unsigned size_t.

Additionally, this patch fixes the case where some iovecs have been
added to the bufferlist and the aio completion has been blocked, but
adding an additional iovec fails because of overflow. This leads to
the UserBufferDeleter trying to unblock the completion on destruction
of the bufferlist but asserting because the completion was never
armed. We avoid this by first computing the total length and checking
for overflows and iovcnt before adding them to the bufferlist.

Signed-off-by: Jonas Pfefferle <pepperjo@japf.ch>
(cherry picked from commit e50405ef857f487bc1c104bbf3e8859ea099a0c4)

diff --git a/src/librbd/librbd.cc b/src/librbd/librbd.cc
index f099143d24600ce33981a34eec54c338570442d0..eb2df58e7987bd637eaa5190d676a41d2c7c4ede 100644 (file)
--- a/src/librbd/librbd.cc
+++ b/src/librbd/librbd.cc
@@ -103,6 +103,40 @@ static auto create_write_raw(librbd::ImageCtx *ictx, const char *buf,
       deleter(new UserBufferDeleter(ictx->cct, aio_completion))));
 }
 
+static int get_iovec_length(const struct iovec *iov, int iovcnt, size_t &len)
+{
+  len = 0;
+
+  if (iovcnt <= 0) {
+    return -EINVAL;
+  }
+
+  for (int i = 0; i < iovcnt; ++i) {
+    const struct iovec &io = iov[i];
+    // check for overflow
+    if (len + io.iov_len < len) {
+      return -EINVAL;
+    }
+    len += io.iov_len;
+  }
+
+  return 0;
+}
+
+static bufferlist iovec_to_bufferlist(librbd::ImageCtx *ictx,
+                                      const struct iovec *iov,
+                                      int iovcnt,
+                                      librbd::io::AioCompletion* aio_completion)
+{
+  bufferlist bl;
+  for (int i = 0; i < iovcnt; ++i) {
+    const struct iovec &io = iov[i];
+    bl.push_back(create_write_raw(ictx, static_cast<char*>(io.iov_base),
+                                  io.iov_len, aio_completion));
+  }
+  return bl;
+}
+
 CephContext* get_cct(IoCtx &io_ctx) {
   return reinterpret_cast<CephContext*>(io_ctx.cct());
 }
@@ -6146,30 +6180,16 @@ extern "C" int rbd_aio_writev(rbd_image_t image, const struct iovec *iov,
   librbd::ImageCtx *ictx = (librbd::ImageCtx *)image;
   librbd::RBD::AioCompletion *comp = (librbd::RBD::AioCompletion *)c;
 
-  // convert the scatter list into a bufferlist
-  auto aio_completion = get_aio_completion(comp);
-  ssize_t len = 0;
-  bufferlist bl;
-  for (int i = 0; i < iovcnt; ++i) {
-    const struct iovec &io = iov[i];
-    len += io.iov_len;
-    if (len < 0) {
-      break;
-    }
-
-    bl.push_back(create_write_raw(ictx, static_cast<char*>(io.iov_base),
-                                  io.iov_len, aio_completion));
-  }
-
-  int r = 0;
-  if (iovcnt <= 0 || len < 0) {
-    r = -EINVAL;
-  }
+  size_t len;
+  int r = get_iovec_length(iov, iovcnt, len);
 
   tracepoint(librbd, aio_write_enter, ictx, ictx->name.c_str(),
              ictx->snap_name.c_str(), ictx->read_only, off, len, NULL,
              comp->pc);
+
   if (r == 0) {
+    auto aio_completion = get_aio_completion(comp);
+    auto bl = iovec_to_bufferlist(ictx, iov, iovcnt, aio_completion);
     librbd::api::Io<>::aio_write(
       *ictx, aio_completion, off, len, std::move(bl), 0, true);
   }
@@ -6210,18 +6230,8 @@ extern "C" int rbd_aio_readv(rbd_image_t image, const struct iovec *iov,
   librbd::ImageCtx *ictx = (librbd::ImageCtx *)image;
   librbd::RBD::AioCompletion *comp = (librbd::RBD::AioCompletion *)c;
 
-  ssize_t len = 0;
-  for (int i = 0; i < iovcnt; ++i) {
-    len += iov[i].iov_len;
-    if (len < 0) {
-      break;
-    }
-  }
-
-  int r = 0;
-  if (iovcnt == 0 || len < 0) {
-    r = -EINVAL;
-  }
+  size_t len;
+  int r = get_iovec_length(iov, iovcnt, len);
 
   tracepoint(librbd, aio_read_enter, ictx, ictx->name.c_str(),
              ictx->snap_name.c_str(), ictx->read_only, off, len, NULL,

diff --git a/src/test/librbd/test_librbd.cc b/src/test/librbd/test_librbd.cc
index 4bbc2ad869f6cd381783d0e358b0fd37d9e12fe6..839775aa08adcf351f8279c56e7c32c98050c86b 100644 (file)
--- a/src/test/librbd/test_librbd.cc
+++ b/src/test/librbd/test_librbd.cc
@@ -41,6 +41,7 @@
 #include <set>
 #include <thread>
 #include <vector>
+#include <limits>
 
 #include "test/librados/test.h"
 #include "test/librados/test_cxx.h"
@@ -2587,8 +2588,10 @@ TEST_F(TestLibRBD, TestScatterGatherIO)
   ASSERT_EQ(0, rbd_open(ioctx, name.c_str(), &image, NULL));
 
   std::string write_buffer("This is a test");
+  // These iovecs should produce a length overflow
   struct iovec bad_iovs[] = {
-    {.iov_base = NULL, .iov_len = static_cast<size_t>(-1)}
+    {.iov_base = &write_buffer[0], .iov_len = 5},
+    {.iov_base = NULL, .iov_len = std::numeric_limits<size_t>::max()}
   };
   struct iovec write_iovs[] = {
     {.iov_base = &write_buffer[0],  .iov_len = 5},
@@ -2600,7 +2603,7 @@ TEST_F(TestLibRBD, TestScatterGatherIO)
   rbd_completion_t comp;
   rbd_aio_create_completion(NULL, NULL, &comp);
   ASSERT_EQ(-EINVAL, rbd_aio_writev(image, write_iovs, 0, 0, comp));
-  ASSERT_EQ(-EINVAL, rbd_aio_writev(image, bad_iovs, 1, 0, comp));
+  ASSERT_EQ(-EINVAL, rbd_aio_writev(image, bad_iovs, 2, 0, comp));
   ASSERT_EQ(0, rbd_aio_writev(image, write_iovs,
                               sizeof(write_iovs) / sizeof(struct iovec),
                               1<<order, comp));
@@ -2617,7 +2620,7 @@ TEST_F(TestLibRBD, TestScatterGatherIO)
 
   rbd_aio_create_completion(NULL, NULL, &comp);
   ASSERT_EQ(-EINVAL, rbd_aio_readv(image, read_iovs, 0, 0, comp));
-  ASSERT_EQ(-EINVAL, rbd_aio_readv(image, bad_iovs, 1, 0, comp));
+  ASSERT_EQ(-EINVAL, rbd_aio_readv(image, bad_iovs, 2, 0, comp));
   ASSERT_EQ(0, rbd_aio_readv(image, read_iovs,
                              sizeof(read_iovs) / sizeof(struct iovec),
                              1<<order, comp));