[Qemu-devel] [PATCH v4 2.1 4/4] ide: Treat read/write beyond end as invalid

[Markus Armbruster <armbru@redhat.com>]

The block layer fails such reads and writes just fine.  However, they
then get treated like valid operations that fail: the error action
gets executed.  Unwanted; reporting the error to the guest is the only
sensible action.

Reject them before passing them to the block layer.  This bypasses the
error action and I/O accounting.  Not quite correct for DMA, because
DMA can fail after some success, and when that happens, the part that
succeeded isn't counted.  Tolerable, because I/O accounting is an
inconsistent mess anyway.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 hw/ide/core.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/hw/ide/core.c b/hw/ide/core.c
index 3a38f1e..db191a6 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -499,6 +499,18 @@ static void ide_rw_error(IDEState *s) {
     ide_set_irq(s->bus);
 }
 
+static bool ide_sect_range_ok(IDEState *s,
+                              uint64_t sector, uint64_t nb_sectors)
+{
+    uint64_t total_sectors;
+
+    bdrv_get_geometry(s->bs, &total_sectors);
+    if (sector > total_sectors || nb_sectors > total_sectors - sector) {
+        return false;
+    }
+    return true;
+}
+
 static void ide_sector_read_cb(void *opaque, int ret)
 {
     IDEState *s = opaque;
@@ -554,6 +566,11 @@ void ide_sector_read(IDEState *s)
     printf("sector=%" PRId64 "\n", sector_num);
 #endif
 
+    if (!ide_sect_range_ok(s, sector_num, n)) {
+        ide_rw_error(s);
+        return;
+    }
+
     s->iov.iov_base = s->io_buffer;
     s->iov.iov_len  = n * BDRV_SECTOR_SIZE;
     qemu_iovec_init_external(&s->qiov, &s->iov, 1);
@@ -671,6 +688,12 @@ void ide_dma_cb(void *opaque, int ret)
            sector_num, n, s->dma_cmd);
 #endif
 
+    if (!ide_sect_range_ok(s, sector_num, n)) {
+        dma_buf_commit(s);
+        ide_dma_error(s);
+        return;
+    }
+
     switch (s->dma_cmd) {
     case IDE_DMA_READ:
         s->bus->dma->aiocb = dma_bdrv_read(s->bs, &s->sg, sector_num,
@@ -790,6 +813,11 @@ void ide_sector_write(IDEState *s)
         n = s->req_nb_sectors;
     }
 
+    if (!ide_sect_range_ok(s, sector_num, n)) {
+        ide_rw_error(s);
+        return;
+    }
+
     s->iov.iov_base = s->io_buffer;
     s->iov.iov_len  = n * BDRV_SECTOR_SIZE;
     qemu_iovec_init_external(&s->qiov, &s->iov, 1);
-- 
1.9.3