virtio-mmio: Fix irq parsing in command line parameter

When the resource_size_t is 64-bit long, the sscanf() on
the virtio device command line paramter string may return
wrong value because its format was defined as "%u". Fixed
by using an intermediate local value of a known length.

Also added cleaned up the resource creation and added extra
comments to make the parameters parsing easier to follow.

Reported-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 17 insertions, 9 deletions

diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
index 5a0e1d32ce1..634f80bcdbd 100644
--- a/drivers/virtio/virtio_mmio.c
+++ b/drivers/virtio/virtio_mmio.c
@@ -521,25 +521,33 @@ static int vm_cmdline_set(const char *device,
         int err;
         struct resource resources[2] = {};
         char *str;
-        long long int base;
+        long long int base, size;
+        unsigned int irq;
         int processed, consumed = 0;
         struct platform_device *pdev;
 
-        resources[0].flags = IORESOURCE_MEM;
-        resources[1].flags = IORESOURCE_IRQ;
-
-        resources[0].end = memparse(device, &str) - 1;
+        /* Consume "size" part of the command line parameter */
+        size = memparse(device, &str);
 
+        /* Get "@<base>:<irq>[:<id>]" chunks */
         processed = sscanf(str, "@%lli:%u%n:%d%n",
-                        &base, &resources[1].start, &consumed,
+                        &base, &irq, &consumed,
                         &vm_cmdline_id, &consumed);
 
-        if (processed < 2 || processed > 3 || str[consumed])
+        /*
+         * sscanf() must processes at least 2 chunks; also there
+         * must be no extra characters after the last chunk, so
+         * str[consumed] must be '\0'
+         */
+        if (processed < 2 || str[consumed])
                 return -EINVAL;
 
+        resources[0].flags = IORESOURCE_MEM;
         resources[0].start = base;
-        resources[0].end += base;
-        resources[1].end = resources[1].start;
+        resources[0].end = base + size - 1;
+
+        resources[1].flags = IORESOURCE_IRQ;
+        resources[1].start = resources[1].end = irq;
 
         if (!vm_cmdline_parent_registered) {
                 err = device_register(&vm_cmdline_parent);