diff mbox series

Fix: buffer overflow during hvc_alloc().

Message ID 20200405204024.1007843-1-andrew@daynix.com
State New
Headers show
Series Fix: buffer overflow during hvc_alloc(). | expand

Checks

Context Check Description
snowpatch_ozlabs/needsstable success Patch has no Fixes tags
snowpatch_ozlabs/checkpatch warning total: 0 errors, 1 warnings, 1 checks, 37 lines checked
snowpatch_ozlabs/build-pmac32 warning Upstream build failed, couldn't test patch
snowpatch_ozlabs/build-ppc64e success Build succeeded
snowpatch_ozlabs/build-ppc64be success Build succeeded
snowpatch_ozlabs/build-ppc64le success Build succeeded
snowpatch_ozlabs/apply_patch success Successfully applied on branch powerpc/merge (2c0ce4ff35994a7b12cc9879ced52c9e7c2e6667)

Commit Message

Andrew Melnichenko April 5, 2020, 8:40 p.m. UTC
From: Andrew Melnychenko <andrew@daynix.com>

If there is a lot(more then 16) of virtio-console devices
or virtio_console module is reloaded
- buffers 'vtermnos' and 'cons_ops' are overflowed.
In older kernels it overruns spinlock which leads to kernel freezing:
https://bugzilla.redhat.com/show_bug.cgi?id=1786239

Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
---
 drivers/tty/hvc/hvc_console.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

Comments

Andrew Donnellan April 6, 2020, 12:31 a.m. UTC | #1
On 6/4/20 6:40 am, andrew@daynix.com wrote:
> From: Andrew Melnychenko <andrew@daynix.com>
> 
> If there is a lot(more then 16) of virtio-console devices
> or virtio_console module is reloaded
> - buffers 'vtermnos' and 'cons_ops' are overflowed.
> In older kernels it overruns spinlock which leads to kernel freezing:
> https://bugzilla.redhat.com/show_bug.cgi?id=1786239
> 

This Bugzilla report isn't publicly accessible. Can you include a 
relevant summary here and/or make the report publicly viewable?

If it does indeed lead to a kernel freeze, this should be tagged with a 
Fixes: and a Cc: stable@vger.kernel.org.
diff mbox series

Patch

diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index 27284a2dcd2b..436cc51c92c3 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/hvc_console.c
@@ -302,10 +302,6 @@  int hvc_instantiate(uint32_t vtermno, int index, const struct hv_ops *ops)
 	vtermnos[index] = vtermno;
 	cons_ops[index] = ops;
 
-	/* reserve all indices up to and including this index */
-	if (last_hvc < index)
-		last_hvc = index;
-
 	/* check if we need to re-register the kernel console */
 	hvc_check_console(index);
 
@@ -960,13 +956,22 @@  struct hvc_struct *hvc_alloc(uint32_t vtermno, int data,
 		    cons_ops[i] == hp->ops)
 			break;
 
-	/* no matching slot, just use a counter */
-	if (i >= MAX_NR_HVC_CONSOLES)
-		i = ++last_hvc;
+	if (i >= MAX_NR_HVC_CONSOLES) {
+
+		/* find 'empty' slot for console */
+		for (i = 0; i < MAX_NR_HVC_CONSOLES && vtermnos[i] != -1; i++) {
+		}
+
+		/* no matching slot, just use a counter */
+		if (i == MAX_NR_HVC_CONSOLES)
+			i = ++last_hvc + MAX_NR_HVC_CONSOLES;
+	}
 
 	hp->index = i;
-	cons_ops[i] = ops;
-	vtermnos[i] = vtermno;
+	if (i < MAX_NR_HVC_CONSOLES) {
+		cons_ops[i] = ops;
+		vtermnos[i] = vtermno;
+	}
 
 	list_add_tail(&(hp->next), &hvc_structs);
 	mutex_unlock(&hvc_structs_mutex);