Commit 2bd3f899 authored by Peter Maydell's avatar Peter Maydell Committed by Laurent Vivier
Browse files

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 commit 58cfa6c2
for the write syscall, and long before that in 38d840e6
for the read syscall.

Fixes: https://bugs.launchpad.net/qemu/+bug/1810433



Signed-off-by: default avatarPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: default avatarLaurent Vivier <laurent@vivier.eu>
Reviewed-by: default avatarPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190108184900.9654-1-peter.maydell@linaro.org>
Signed-off-by: default avatarLaurent Vivier <laurent@vivier.eu>
parent bd8ed485

linux-user/syscall.c

+18 −4
Original line number Diff line number Diff line
@@ -9716,8 +9716,15 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1, 
            arg4 = arg5;

            arg5 = arg6;

        }

        if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0)))

        if (arg2 == 0 && arg3 == 0) {

            /* Special-case NULL buffer and zero length, which should succeed */

            p = 0;

        } else {

            p = lock_user(VERIFY_WRITE, arg2, arg3, 0);

            if (!p) {

                return -TARGET_EFAULT;

            }

        }

        ret = get_errno(pread64(arg1, p, arg3, target_offset64(arg4, arg5)));

        unlock_user(p, arg2, ret);

        return ret;
@@ -9726,8 +9733,15 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1, 
            arg4 = arg5;

            arg5 = arg6;

        }

        if (!(p = lock_user(VERIFY_READ, arg2, arg3, 1)))

        if (arg2 == 0 && arg3 == 0) {

            /* Special-case NULL buffer and zero length, which should succeed */

            p = 0;

        } else {

            p = lock_user(VERIFY_READ, arg2, arg3, 1);

            if (!p) {

                return -TARGET_EFAULT;

            }

        }

        ret = get_errno(pwrite64(arg1, p, arg3, target_offset64(arg4, arg5)));

        unlock_user(p, arg2, 0);

        return ret;