Le 09/06/2016 à 16:09, Peter Maydell a écrit : > 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.mayd...@linaro.org>
Reviewed-by: Laurent Vivier <laur...@vivier.eu> > --- > linux-user/signal.c | 13 +++++++++++-- > 1 file changed, 11 insertions(+), 2 deletions(-) > > diff --git a/linux-user/signal.c b/linux-user/signal.c > index 61c1145..37fb60f 100644 > --- a/linux-user/signal.c > +++ b/linux-user/signal.c > @@ -281,6 +281,14 @@ static inline void > host_to_target_siginfo_noswap(target_siginfo_t *tinfo, > 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 > @@ -400,8 +408,9 @@ static void tswap_siginfo(target_siginfo_t *tinfo, > > 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. */ >