Re: [libvirt] [PATCH] qemu: avoid pass null pointer as an argument

On 08/04/2011 09:31 AM, Alex Jia wrote: > In fact, 'pos' is always -1, this reason is because qemuProcessStart > function > assigns -1 to 'pos' variable then call qemuProcessWaitForMonitor, Actually, qemuProcessStart always calls qemuProcessWaitForMonitor with non-negative pos (pos was set by lseek()ing to the end of the log file). > meanwhile, > qemuProcessAttach function also call qemuProcessWaitForMonitor and > directly > pass -1 as an argument, so if (pos != -1) statement can't been run > for ever, Rather, this merely means that the if (pos != -1) statement wasn't run when called by qemuProcessAttach. > it also means we can't allocate memory to 'buf' variable, that is, > 'buf' is > a initial value NULL, however, the function > qemuProcessReadLogFD(logfd, buf, buf_size, strlen(buf)) will be called > on 'cleanup' section, null pointer passed as an argument. > > * src/qemu/qemu_process.c: avoid null pointer passed as an argument to a > 'nonnull' parameter. We definitely have a bug here, but this is not the right fix. The bug is that the cleanup: label is trying to read from logfd if the vm crashed, without having opened logfd in the qemuProcessAttach case. I think the more appropriate patch is this: diff --git i/src/qemu/qemu_process.c w/src/qemu/qemu_process.c index 8508ff6..1eea45f 100644 --- i/src/qemu/qemu_process.c +++ w/src/qemu/qemu_process.c @@ -1214,7 +1214,7 @@ qemuProcessWaitForMonitor(struct qemud_driver* driver, cleanup: virHashFree(paths); - if (kill(vm->pid, 0) == -1 && errno == ESRCH) { + if (pos != -1 && kill(vm->pid, 0) == -1 && errno == ESRCH) { /* VM is dead, any other error raised in the interim is probably * not as important as the qemu cmdline output */ qemuProcessReadLogFD(logfd, buf, buf_size, strlen(buf));