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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>
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@ -278,6 +278,14 @@ static inline void host_to_target_siginfo_noswap(target_siginfo_t *tinfo,
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tinfo->si_errno = 0;
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tinfo->si_errno = 0;
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tinfo->si_code = info->si_code;
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tinfo->si_code = info->si_code;
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/* This memset serves two purposes:
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* (1) ensure we don't leak random junk to the guest later
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* (2) placate false positives from gcc about fields
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* being used uninitialized if it chooses to inline both this
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* function and tswap_siginfo() into host_to_target_siginfo().
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*/
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memset(tinfo->_sifields._pad, 0, sizeof(tinfo->_sifields._pad));
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/* This is awkward, because we have to use a combination of
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/* This is awkward, because we have to use a combination of
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* the si_code and si_signo to figure out which of the union's
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* the si_code and si_signo to figure out which of the union's
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* members are valid. (Within the host kernel it is always possible
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* members are valid. (Within the host kernel it is always possible
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@ -397,8 +405,9 @@ static void tswap_siginfo(target_siginfo_t *tinfo,
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void host_to_target_siginfo(target_siginfo_t *tinfo, const siginfo_t *info)
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void host_to_target_siginfo(target_siginfo_t *tinfo, const siginfo_t *info)
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{
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{
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host_to_target_siginfo_noswap(tinfo, info);
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target_siginfo_t tgt_tmp;
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tswap_siginfo(tinfo, tinfo);
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host_to_target_siginfo_noswap(&tgt_tmp, info);
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tswap_siginfo(tinfo, &tgt_tmp);
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}
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}
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/* XXX: we support only POSIX RT signals are used. */
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/* XXX: we support only POSIX RT signals are used. */
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