Chris Lalancette wrote:
On 12/14/2009 02:48 PM, Jim Meyering wrote:
From: Jim Meyering <meyering@redhat.com> Date: Mon, 14 Dec 2009 12:05:38 +0100 Subject: [PATCH] node_device_driver.c: don't write beyond EOB for 4K-byte symlink
* src/node_device/node_device_driver.c (update_driver_name): The previous code would write one byte beyond the end of the 4KiB stack buffer when presented with a symlink value of exactly that length (very unlikely). Remove the automatic buffer and use virFileResolveLink in place of readlink. Suggested by Daniel Veillard. --- src/node_device/node_device_driver.c | 7 +++---- 1 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/src/node_device/node_device_driver.c b/src/node_device/node_device_driver.c index f083f16..ecbac0f 100644 --- a/src/node_device/node_device_driver.c +++ b/src/node_device/node_device_driver.c @@ -78,10 +78,9 @@ static int update_driver_name(virConnectPtr conn, virNodeDeviceObjPtr dev) { char *driver_link = NULL; - char devpath[PATH_MAX]; + char *devpath; char *p; int ret = -1; - int n;
VIR_FREE(dev->def->driver);
@@ -97,12 +96,11 @@ static int update_driver_name(virConnectPtr conn, goto cleanup; }
- if ((n = readlink(driver_link, devpath, sizeof devpath)) < 0) { + if (virFileResolveLink(driver_link, &devpath) < 0) {
FYI; I found out today that virFileResolveLink() doesn't work on filesystems backed by sysfs (which unfortunately this code path is). The problem is that sysfs doesn't follow the POSIX-specified behavior of placing the size of the name of the real path in st.st_size; instead, on sysfs, st.st_size for symlinks is *always* 0 (at least on my F-12 box here). So this code path is probably broken now. DV said he will take a look at putting a patch together to make virFileResolveLink() handle the 0 case.
Good point. Don't bother rolling your own. I'll prepare a patch to use gnulib's areadlink module.