Re: [libvirt] [PATCH] domtop: Properly free cpu status

So, in the example the cpu stats are collected within a function called do_top. At the beginning of the function we ask the daemon for how much vCPUs can we get stats, and how many stats for a vCPU can we get. This is because it's how our API works - users are required to preallocate a chunk of memory for the results. Now, at the end, we try to free the allocated array, but we are not doing it correctly. There's this virTypedParamsFree() function which gets a pointer to the array and the length of the array. However, if there was an error in getting vCPU stats we pass a negative number instead of the originally computed value. This flaw results in SIGSEGV: libvirt: QEMU Driver error : Requested operation is not valid: domain is not running ERROR do_top:333 : Unable to get cpu stats ==29201== Invalid read of size 4 ==29201== at 0x4F1DF8B: virTypedParamsClear (virtypedparam.c:1145) ==29201== by 0x4F1DFEB: virTypedParamsFree (virtypedparam.c:1165) ==29201== by 0x4023C3: do_top (domtop.c:349) ==29201== by 0x40260B: main (domtop.c:386) ==29201== Address 0x131cd7c0 is 16 bytes after a block of size 768 alloc'd ==29201== at 0x4C2C070: calloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so) ==29201== by 0x401FF1: do_top (domtop.c:295) ==29201== by 0x40260B: main (domtop.c:386) Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com&gt; --- examples/domtop/domtop.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/examples/domtop/domtop.c b/examples/domtop/domtop.c index e50988e..2283994 100644 --- a/examples/domtop/domtop.c +++ b/examples/domtop/domtop.c @@ -346,8 +346,8 @@ do_top(virConnectPtr conn, ret = 0; cleanup: - virTypedParamsFree(now_params, now_nparams * max_id); - virTypedParamsFree(then_params, then_nparams * max_id); + virTypedParamsFree(now_params, nparams * max_id); + virTypedParamsFree(then_params, nparams * max_id);