mirror of https://gitlab.com/qemu-project/qemu
linux-user: make pwrite64/pread64(fd, NULL, 0, offset) return 0
Linux returns success if pwrite64() or pread64() are called with a zero length NULL buffer, but QEMU was returning -TARGET_EFAULT. This is the same bug that we fixed in commit58cfa6c2e6
for the write syscall, and long before that in38d840e679
for the read syscall. Fixes: https://bugs.launchpad.net/qemu/+bug/1810433 Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Laurent Vivier <laurent@vivier.eu> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> Message-Id: <20190108184900.9654-1-peter.maydell@linaro.org> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
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@ -9716,8 +9716,15 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
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arg4 = arg5;
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arg4 = arg5;
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arg5 = arg6;
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arg5 = arg6;
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}
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}
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if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0)))
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if (arg2 == 0 && arg3 == 0) {
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/* Special-case NULL buffer and zero length, which should succeed */
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p = 0;
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} else {
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p = lock_user(VERIFY_WRITE, arg2, arg3, 0);
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if (!p) {
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return -TARGET_EFAULT;
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return -TARGET_EFAULT;
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}
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}
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ret = get_errno(pread64(arg1, p, arg3, target_offset64(arg4, arg5)));
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ret = get_errno(pread64(arg1, p, arg3, target_offset64(arg4, arg5)));
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unlock_user(p, arg2, ret);
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unlock_user(p, arg2, ret);
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return ret;
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return ret;
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@ -9726,8 +9733,15 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
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arg4 = arg5;
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arg4 = arg5;
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arg5 = arg6;
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arg5 = arg6;
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}
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}
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if (!(p = lock_user(VERIFY_READ, arg2, arg3, 1)))
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if (arg2 == 0 && arg3 == 0) {
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/* Special-case NULL buffer and zero length, which should succeed */
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p = 0;
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} else {
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p = lock_user(VERIFY_READ, arg2, arg3, 1);
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if (!p) {
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return -TARGET_EFAULT;
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return -TARGET_EFAULT;
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}
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}
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ret = get_errno(pwrite64(arg1, p, arg3, target_offset64(arg4, arg5)));
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ret = get_errno(pwrite64(arg1, p, arg3, target_offset64(arg4, arg5)));
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unlock_user(p, arg2, 0);
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unlock_user(p, arg2, 0);
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return ret;
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return ret;
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