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udevListInterfaces: Honour array length for zero-length NULL arrays (CVE-2024-8235)

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The refactor of 'udevListInterfacesByStatus()' which attempted to make
it usable as backend for 'udevNumOfInterfacesByStatus()' neglected to
consider the corner case of 'g_new0(..., 0)' returning NULL if the user
actually requests 0 elements.

As the code was modified to report the full number of interfaces in the
system when the list of names is NULL, the RPC code would be asked to
serialize a NULL-list of interface names with declared lenth of 1+
causing a crash.

To fix this corner case we make callers pass '-1' as @names_len (it's
conveniently an 'int' due to RPC type usage) if they don't wish to fetch
the actual list and convert all decisions to be done on @names_len being
non-negative instead of @names being non-NULL.

CVE-2024-8235

Fixes: bc596f2751
Resolves: https://issues.redhat.com/browse/RHEL-55373
Reported-by: Yanqiu Zhang  <yanqzhan@redhat.com>
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
This commit is contained in:
Peter Krempa 2024-08-21 15:18:31 +02:00
parent 3284b0d8cd
commit 8dfb12cb77
1 changed files with 8 additions and 6 deletions
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14
src/interface/interface_backend_udev.c
View File

@ -143,12 +143,13 @@ udevGetDevices(struct udev *udev, virUdevStatus status)
* *
* @conn: connection object * @conn: connection object
* @names: optional pointer to array to be filled with interface names * @names: optional pointer to array to be filled with interface names
* @names_len: size of @names * @names_len: size of @names, -1 if only number of interfaces is required (@names is then ignored)
* @status: status of interfaces to be listed * @status: status of interfaces to be listed
* @filter: ACL filter function * @filter: ACL filter function
* *
* Lists interfaces with status matching @status filling them into @names (if * Lists interfaces with status matching @status filling them into @names (if
* non-NULL) and returns the number of such interfaces. * @names_len is positive, caller is expected to pass a properly sized array)
* and returns the number of such interfaces.
* *
* In case of an error -1 is returned and no interfaces are filled into @names. * In case of an error -1 is returned and no interfaces are filled into @names.
*/ */
@ -189,7 +190,7 @@ udevListInterfacesByStatus(virConnectPtr conn,
g_autoptr(virInterfaceDef) def = NULL; g_autoptr(virInterfaceDef) def = NULL;
/* Ensure we won't exceed the size of our array */ /* Ensure we won't exceed the size of our array */
if (names && count >= names_len) if (names_len >= 0 && count >= names_len)
break; break;
path = udev_list_entry_get_name(dev_entry); path = udev_list_entry_get_name(dev_entry);
@ -204,7 +205,8 @@ udevListInterfacesByStatus(virConnectPtr conn,
def = udevGetMinimalDefForDevice(dev); def = udevGetMinimalDefForDevice(dev);
if (filter(conn, def)) { if (filter(conn, def)) {
if (names) /* Fill the array only if caller want's it */
if (names_len >= 0)
names[count] = g_strdup(name); names[count] = g_strdup(name);
count++; count++;
} }
@ -224,7 +226,7 @@ udevConnectNumOfInterfaces(virConnectPtr conn)
if (virConnectNumOfInterfacesEnsureACL(conn) < 0) if (virConnectNumOfInterfacesEnsureACL(conn) < 0)
return -1; return -1;
return udevListInterfacesByStatus(conn, NULL, 0, VIR_UDEV_IFACE_ACTIVE, return udevListInterfacesByStatus(conn, NULL, -1, VIR_UDEV_IFACE_ACTIVE,
virConnectNumOfInterfacesCheckACL); virConnectNumOfInterfacesCheckACL);
} }
@ -247,7 +249,7 @@ udevConnectNumOfDefinedInterfaces(virConnectPtr conn)
if (virConnectNumOfDefinedInterfacesEnsureACL(conn) < 0) if (virConnectNumOfDefinedInterfacesEnsureACL(conn) < 0)
return -1; return -1;
return udevListInterfacesByStatus(conn, NULL, 0, VIR_UDEV_IFACE_INACTIVE, return udevListInterfacesByStatus(conn, NULL, -1, VIR_UDEV_IFACE_INACTIVE,
virConnectNumOfDefinedInterfacesCheckACL); virConnectNumOfDefinedInterfacesCheckACL);
} }