linux-user: Avoid possible misalignment in host_to_target_siginfo()
host_to_target_siginfo() is implemented by a combination of
host_to_target_siginfo_noswap() followed by tswap_siginfo().
The first of these two functions assumes that the target_siginfo_t
it is writing to is correctly aligned, but the pointer passed
into host_to_target_siginfo() is directly from the guest and
might be misaligned. Use a local variable to avoid this problem.
(tswap_siginfo() does now correctly handle a misaligned destination.)
We have to add a memset() to host_to_target_siginfo_noswap()
to avoid some false positive "may be used uninitialized" warnings
from gcc about subfields of the _sifields union if it chooses to
inline both tswap_siginfo() and host_to_target_siginfo_noswap()
into host_to_target_siginfo().
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Peter Maydell <riku.voipio@linaro.org>
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 1dadddf..e2d55ff 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -278,6 +278,14 @@
tinfo->si_errno = 0;
tinfo->si_code = info->si_code;
+ /* This memset serves two purposes:
+ * (1) ensure we don't leak random junk to the guest later
+ * (2) placate false positives from gcc about fields
+ * being used uninitialized if it chooses to inline both this
+ * function and tswap_siginfo() into host_to_target_siginfo().
+ */
+ memset(tinfo->_sifields._pad, 0, sizeof(tinfo->_sifields._pad));
+
/* This is awkward, because we have to use a combination of
* the si_code and si_signo to figure out which of the union's
* members are valid. (Within the host kernel it is always possible
@@ -397,8 +405,9 @@
void host_to_target_siginfo(target_siginfo_t *tinfo, const siginfo_t *info)
{
- host_to_target_siginfo_noswap(tinfo, info);
- tswap_siginfo(tinfo, tinfo);
+ target_siginfo_t tgt_tmp;
+ host_to_target_siginfo_noswap(&tgt_tmp, info);
+ tswap_siginfo(tinfo, &tgt_tmp);
}
/* XXX: we support only POSIX RT signals are used. */
