On Fri, Jan 20, 2017 at 10:42:48AM +0100, Michal Privoznik wrote:
When working with symlinks it is fairly easy to get into a loop.
Don't.
Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
src/qemu/qemu_domain.c | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 8cbfb2d16..448583313 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -6954,9 +6954,10 @@ qemuDomainGetPreservedMounts(virQEMUDriverPtr driver,
static int
-qemuDomainCreateDevice(const char *device,
- const char *path,
- bool allow_noent)
+qemuDomainCreateDeviceRecursive(const char *device,
+ const char *path,
+ bool allow_noent,
+ unsigned int ttl)
{
char *devicePath = NULL;
char *target = NULL;
@@ -6968,6 +6969,13 @@ qemuDomainCreateDevice(const char *device,
char *tcon = NULL;
#endif
+ if (!ttl) {
+ virReportSystemError(ELOOP,
+ _("Too many levels of symbolic links: %s"),
+ device);
+ return ret;
+ }
+
if (lstat(device, &sb) < 0) {
if (errno == ENOENT && allow_noent) {
/* Ignore non-existent device. */
@@ -7057,7 +7065,8 @@ qemuDomainCreateDevice(const char *device,
tmp = NULL;
}
- if (qemuDomainCreateDevice(target, path, allow_noent) < 0)
+ if (qemuDomainCreateDeviceRecursive(target, path,
+ allow_noent, ttl - 1) < 0)
goto cleanup;
} else {
if (create &&
@@ -7128,6 +7137,17 @@ qemuDomainCreateDevice(const char *device,
}
+static int
+qemuDomainCreateDevice(const char *device,
+ const char *path,
+ bool allow_noent)
+{
+ long symloop_max = sysconf(_SC_SYMLOOP_MAX);
+
+ return qemuDomainCreateDeviceRecursive(device, path,
+ allow_noent, symloop_max);
So you are taking 'long' that can, officially, be '-1' and pass it to a function as unsigned int. Having a maximum is nice, I have no idea why on my system there is no limit apparently (sysconf() returns -1 with no errno set), but if the system doesn't report any (like my case above) it effectively makes the SYMLOOP_MAX = UINT_MAX in this codepath. Should we avoid that or just let it be? This way it's still better than unlimited, so ACK to this version, but I just wanted a (short) discussion about this.
+} + static int qemuDomainPopulateDevices(virQEMUDriverPtr driver, -- 2.11.0 -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
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