Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3343
The Linux kernel writes back the remaining timeout for select-family syscalls in poll_select_finish(). If that writeback fails, it keeps the original return value. However, QEMU only writes back the timeout on success. If the writeback fails, QEMU returns -TARGET_EFAULT. This can lose the remaining timeout and change the return value. Update do_select(), do_pselect6(), and do_ppoll() to always write back the timeout to match the Linux kernel's behavior. If the timeout writeback fails, keep the original return value. Tested with the issue reproducer. Signed-off-by: Sun Haoyu <[email protected]> --- Changes since v1: - write back the timeout in all cases - handle do_select() too - keep the original return value if timeout writeback fails linux-user/syscall.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-) diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 064bc604c9..877a3b8bb6 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -1394,13 +1394,12 @@ static abi_long do_select(int n, return -TARGET_EFAULT; if (efd_addr && copy_to_user_fdset(efd_addr, &efds, n)) return -TARGET_EFAULT; - - if (target_tv_addr) { - tv.tv_sec = ts.tv_sec; - tv.tv_usec = ts.tv_nsec / 1000; - if (copy_to_user_timeval(target_tv_addr, &tv)) { - return -TARGET_EFAULT; - } + } + if (target_tv_addr) { + tv.tv_sec = ts.tv_sec; + tv.tv_usec = ts.tv_nsec / 1000; + if (copy_to_user_timeval(target_tv_addr, &tv)) { + return ret; } } @@ -1529,16 +1528,18 @@ static abi_long do_pselect6(abi_long arg1, abi_long arg2, abi_long arg3, if (efd_addr && copy_to_user_fdset(efd_addr, &efds, n)) { return -TARGET_EFAULT; } + } + if (ts_addr) { if (time64) { - if (ts_addr && host_to_target_timespec64(ts_addr, &ts)) { - return -TARGET_EFAULT; + if (host_to_target_timespec64(ts_addr, &ts)) { + return ret; } } else { - if (ts_addr && host_to_target_timespec(ts_addr, &ts)) { - return -TARGET_EFAULT; + if (host_to_target_timespec(ts_addr, &ts)) { + return ret; } } - } + } return ret; } #endif @@ -1606,14 +1607,14 @@ static abi_long do_ppoll(abi_long arg1, abi_long arg2, abi_long arg3, if (set) { finish_sigsuspend_mask(ret); } - if (!is_error(ret) && arg3) { + if (arg3) { if (time64) { if (host_to_target_timespec64(arg3, timeout_ts)) { - return -TARGET_EFAULT; + return ret; } } else { if (host_to_target_timespec(arg3, timeout_ts)) { - return -TARGET_EFAULT; + return ret; } } } -- 2.53.0
