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Re: [libvirt] [PATCH] virsh: avoid uninitialized memory usage

On 04/19/2012 04:40 PM, Alex Jia wrote:
On 04/19/2012 04:19 PM, Wen Congyang wrote:
At 04/19/2012 04:09 PM, Alex Jia Wrote:
Detected by valgrind.

* tools/virsh.c (cmdBlockPull): fix uninitialized memory usage.

* How to reproduce?
$ qemu-img create /var/lib/libvirt/images/test 1M
$ cat>  /tmp/test.xml<<EOF
<domain type='qemu'>
<type arch='x86_64'>hvm</type>
<boot dev='hd'/>
<disk type='file' device='disk'>
<driver name='qemu' type='raw'/>
<source file='/var/lib/libvirt/images/test'/>
<target dev='vda' bus='virtio'/>
<input type='mouse' bus='ps2'/>
<graphics type='spice' autoport='yes' listen=''/>
$ virsh define /tmp/test.xml
$ valgrind -v virsh blockpull test /var/lib/libvirt/images/test --wait

actual result:

==10906== 1 errors in context 1 of 1:
==10906== Syscall param rt_sigaction(act->sa_flags) points to uninitialised byte(s)
==10906==    at 0x39CF80F5BE: __libc_sigaction (sigaction.c:67)
==10906==    by 0x43016C: cmdBlockPull (virsh.c:7638)
==10906==    by 0x4150D4: vshCommandRun (virsh.c:18574)
==10906==    by 0x425E73: main (virsh.c:20178)
==10906==  Address 0x7fefffae8 is on thread 1's stack

Signed-off-by: Alex Jia<ajia redhat com>
  tools/virsh.c |    1 +
  1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/tools/virsh.c b/tools/virsh.c
index 95ed7bc..4e4ca57 100644
--- a/tools/virsh.c
+++ b/tools/virsh.c
@@ -7634,6 +7634,7 @@ cmdBlockPull(vshControl *ctl, const vshCmd *cmd)

          intCaught = 0;
          sig_action.sa_sigaction = vshCatchInt;
+        sigemptyset((sigset_t *)&sig_action.sa_flags);
Why using sigemptyset here? You should use 'sig_action.sa_flags = 0'.
Yeah, I think 'sig_action.sa_flags = 0' is right, but I don't know what the difference are,
could you explain more?
The sigemptyset() function manipulates sets of signals and initialize signal set to be empty.
'sig_action.sa_flags = 0' is right and enough in here.


Wen Congyang


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