On 3/16/20 1:09 PM, Philippe Mathieu-Daudé wrote:
On 3/16/20 5:07 PM, Stefan Hajnoczi wrote:
gcc (GCC) 9.2.1 20190827 (Red Hat 9.2.1-1) with sanitizers enabled
reports the following error:
CC migration/global_state.o
In file included from /usr/include/string.h:495,
from /home/stefanha/qemu/include/qemu/osdep.h:101,
from migration/global_state.c:13:
In function ‘strncpy’,
inlined from ‘global_state_store_running’ at
migration/global_state.c:47:5:
/usr/include/bits/string_fortified.h:106:10: error:
‘__builtin_strncpy’ specified bound 100 equals destination size
[-Werror=stringop-truncation]
106 | return __builtin___strncpy_chk (__dest, __src, __len,
__bos (__dest));
|
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Use pstrcpy() instead of strncpy(). It is guaranteed to NUL-terminate
strings.
There was a long discussion 1 year ago with it, and Eric suggested to
use strpadcpy after the assert() and I sent this patch:
https://www.mail-archive.com/qemu-block@nongnu.org/msg44925.html
Not sure what's best.
strncpy() pads the tail, guaranteeing that for our fixed-size buffer, we
guarantee the contents of all bytes in the buffer. pstrcpy() does not
(but pstrcpy() can be followed up with a memset() to emulate the
remaining effects of strncpy() - at which point you have reimplemented
strpadcpy).
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
migration/global_state.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/migration/global_state.c b/migration/global_state.c
index 25311479a4..cbe07f21a8 100644
--- a/migration/global_state.c
+++ b/migration/global_state.c
@@ -44,8 +44,8 @@ void global_state_store_running(void)
{
const char *state = RunState_str(RUN_STATE_RUNNING);
assert(strlen(state) < sizeof(global_state.runstate));
- strncpy((char *)global_state.runstate,
- state, sizeof(global_state.runstate));
+ pstrcpy((char *)global_state.runstate,
+ sizeof(global_state.runstate), state);
Can we guarantee that the padding bytes have been previously set to 0,
or do we need to go the extra mile with a memset() or strpadcpy() to
guarantee that we have set the entire buffer?
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
