Processed: Re: Bug#1042562: libc6: broken utmp handling in 32-bit programs with 64-bit time_t
Processing control commands: > forwarded -1 https://sourceware.org/bugzilla/show_bug.cgi?id=30701 Bug #1042562 [libc6] libc6: broken utmp handling in 32-bit programs with 64-bit time_t Set Bug forwarded-to-address to 'https://sourceware.org/bugzilla/show_bug.cgi?id=30701'. -- 1042562: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1042562 Debian Bug Tracking System Contact ow...@bugs.debian.org with problems
Bug#1042562: libc6: broken utmp handling in 32-bit programs with 64-bit time_t
Control: forwarded -1 https://sourceware.org/bugzilla/show_bug.cgi?id=30701
On 2023-07-30 13:25 +0200, Sven Joachim wrote:
> Package: libc6
> Version: 2.37-6
> Tags: upstream
>
> The utmp(5) interface has broken its compatibility in 32-bit programs
> built with -D_TIME_BITS=64. In bits/utmpx.h we see this:
>
> ,
> | /* The fields ut_session and ut_tv must be the same size when compiled
> |32- and 64-bit. This allows files and shared memory to be shared
> |between 32- and 64-bit applications. */
> | #if __WORDSIZE_TIME64_COMPAT32
> | __int32_t ut_session; /* Session ID, used for windowing. */
> | struct
> | {
> | __int32_t tv_sec; /* Seconds. */
> | __int32_t tv_usec; /* Microseconds. */
> | } ut_tv; /* Time entry was made. */
> | #else
> | long int ut_session; /* Session ID, used for windowing. */
> | struct timeval ut_tv; /* Time entry was made. */
> | #endif
> `
>
> The definition of __WORDSIZE_TIME64_COMPAT32 can be found in bits/wordsize.h:
>
> ,
> | #ifdef __x86_64__
> | # define __WORDSIZE_TIME64_COMPAT32 1
> | /* Both x86-64 and x32 use the 64-bit system call interface. */
> | # define __SYSCALL_WORDSIZE 64
> | #else
> | # define __WORDSIZE_TIME64_COMPAT32 0
> | #endif
> `
>
> So on i386 (and I suppose on other 32-bit architectures except x32)
> ut_tv is of struct timeval, and ut_tv.tv_sec is of time_t, which is
> actually a 64-bit integer in programs built with -D_TIME_BITS=64.
>
> One example where this already has caused problems is the who(1) program
> which has opted in for -D_TIME_BITS=64, see #1027135.
I had brought the "who" problem to the attention of the coreutils
developers[1], and they have now reported the issue in the Sourceware
Bugzilla.
Cheers,
Sven
1. https://debbugs.gnu.org/64937
Bug#1042562: libc6: broken utmp handling in 32-bit programs with 64-bit time_t
Package: libc6
Version: 2.37-6
Tags: upstream
The utmp(5) interface has broken its compatibility in 32-bit programs
built with -D_TIME_BITS=64. In bits/utmpx.h we see this:
,
| /* The fields ut_session and ut_tv must be the same size when compiled
|32- and 64-bit. This allows files and shared memory to be shared
|between 32- and 64-bit applications. */
| #if __WORDSIZE_TIME64_COMPAT32
| __int32_t ut_session; /* Session ID, used for windowing. */
| struct
| {
| __int32_t tv_sec; /* Seconds. */
| __int32_t tv_usec;/* Microseconds. */
| } ut_tv;/* Time entry was made. */
| #else
| long int ut_session;/* Session ID, used for windowing. */
| struct timeval ut_tv; /* Time entry was made. */
| #endif
`
The definition of __WORDSIZE_TIME64_COMPAT32 can be found in bits/wordsize.h:
,
| #ifdef __x86_64__
| # define __WORDSIZE_TIME64_COMPAT32 1
| /* Both x86-64 and x32 use the 64-bit system call interface. */
| # define __SYSCALL_WORDSIZE 64
| #else
| # define __WORDSIZE_TIME64_COMPAT32 0
| #endif
`
So on i386 (and I suppose on other 32-bit architectures except x32)
ut_tv is of struct timeval, and ut_tv.tv_sec is of time_t, which is
actually a 64-bit integer in programs built with -D_TIME_BITS=64.
One example where this already has caused problems is the who(1) program
which has opted in for -D_TIME_BITS=64, see #1027135. Once programs
start to _write_ utmp entries with a 64-bit ut_tv.tv_sec rather than
merely reading them, things could become more interesting. :-(
-- System Information:
Debian Release: trixie/sid
APT prefers unstable
APT policy: (500, 'unstable'), (101, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
