On Wed, Jun 20, 2018 at 6:55 PM, Viacheslav Dubeyko slava@dubeyko.com wrote:
On Tue, 2018-06-19 at 21:42 +0200, Arnd Bergmann wrote:
On Tue, Jun 19, 2018 at 7:03 PM, Viacheslav Dubeyko slava@dubeyko.com wrote:
We never followed that interpretation in Linux though. As I wrote, on 64-bit machines, these two calculations (hfs and hfs+, respectively)
#define __hfs_m_to_utime(sec) (be32_to_cpu(sec) - 2082844800U + sys_tz.tz_minuteswest * 60) #define __hfsp_mt2ut(t) (be32_to_cpu(t) - 2082844800U)
just wrap around when reading the timestamps before 1970 from disk. On 32-bit machines they get wrapped another time when we assign them to a signed 32-bit time_t.
The whole patchset looks reasonable for me. I simply guess what the correct behaviour of HFS/HFS+ file system driver could look like for the case of achieving 2040 year. So, maybe the good way could be to mount in the READ-ONLY mode. What do you think?
We've discussed doing that in VFS before, this is something we need to revisit, but I'd like to do it in common code rather than in every file system with a particular limit.
Deepa has a patch set to introduce minimum/maximum timestamps in the superblock for this. We definitely want to use that for limiting the range of utimensat() arguments from user space, and the idea we had discussed in the past was to have a way to enforce read-only mounting of file systems that cannot write current i_mtime values past a certain (user-defined) future date.
We actually need something like that soon, as there are some organizations that want to support super-long service lifetimes for Linux systems (e.g. cars, industrial machines, ...) and want an early-fail behavior to ensure that everything that works today can in principle keep working for the foreseeable future, while everything that is known to break can be forced to break already.
This is clearly not a priority for HFS in particular, but there is no reason for HFS to be different from ext3 here, which has a similar problem (timestamps are defined to range from 1902 to 2038).
/* time macros: convert between 1904-2040 and 1970-2106 range,
- pre-1970 timestamps are interpreted as post-2038 times after
wrap-around */ -#define __hfsp_mt2ut(t) (be32_to_cpu(t) - 2082844800U) +#define __hfsp_mt2ut(t) ((time64_t)be32_to_cpu(t) - 2082844800U) #define __hfsp_ut2mt(t) (cpu_to_be32(t + 2082844800U))
/* compatibility */
I can submit that separately so that it can get backported into stable kernels if you like, with the type changes as a follow-up on top.
Sounds good.
Ok, I'll send an updated version with that patch first then.
Arnd