lp:~ubuntu-kernel-test/ubuntu/+source/linux/+git/linus--linux

Author: Linus Torvalds
Author Date: 2023-11-19 23:02:14 UTC

Linux 6.7-rc2

Author: Linus Torvalds
Author Date: 2023-05-03 17:13:41 UTC

x86-64: mm: clarify the 'positive addresses' user address rules

Dave Hansen found the "(long) addr >= 0" code in the x86-64 access_ok
checks somewhat confusing, and suggested using a helper to clarify what
the code is doing.

So this does exactly that: clarifying what the sign bit check is all
about, by adding a helper macro that makes it clear what it is testing.

This also adds some explicit comments talking about how even with LAM
enabled, any addresses with the sign bit will still GP-fault in the
non-canonical region just above the sign bit.

This is all what allows us to do the user address checks with just the
sign bit, and furthermore be a bit cavalier about accesses that might be
done with an additional offset even past that point.

(And yes, this talks about 'positive' even though zero is also a valid
user address and so technically we should call them 'non-negative'. But
I don't think using 'non-negative' ends up being more understandable).

Suggested-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Linus Torvalds
Author Date: 2023-04-20 22:13:50 UTC

x86: rewrite '__copy_user_nocache' function

I didn't really want to do this, but as part of all the other changes to
the user copy loops, I've been looking at this horror.

I tried to clean it up multiple times, but every time I just found more
problems, and the way it's written, it's just too hard to fix them.

For example, the code is written to do quad-word alignment, and will use
regular byte accesses to get to that point. That's fairly simple, but
it means that any initial 8-byte alignment will be done with cached
copies.

However, the code then is very careful to do any 4-byte _tail_ accesses
using an uncached 4-byte write, and that was claimed to be relevant in
commit a82eee742452 ("x86/uaccess/64: Handle the caching of 4-byte
nocache copies properly in __copy_user_nocache()").

So if you do a 4-byte copy using that function, it carefully uses a
4-byte 'movnti' for the destination. But if you were to do a 12-byte
copy that is 4-byte aligned, it would _not_ do a 4-byte 'movnti'
followed by a 8-byte 'movnti' to keep it all uncached.

Instead, it would align the destination to 8 bytes using a
byte-at-a-time loop, and then do a 8-byte 'movnti' for the final 8
bytes.

The main caller that cares is __copy_user_flushcache(), which knows
about this insanity, and has odd cases for it all. But I just can't
deal with looking at this kind of "it does one case right, and another
related case entirely wrong".

And the code really wasn't fixable without hard drugs, which I try to
avoid.

So instead, rewrite it in a form that hopefully not only gets this
right, but is a bit more maintainable. Knock wood.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Linus Torvalds
Author Date: 2022-10-29 18:45:07 UTC

mm: delay rmap removal until after TLB flush

When we remove a page table entry, we are very careful to only free the
page after we have flushed the TLB, because other CPUs could still be
using the page through stale TLB entries until after the flush.

However, we have removed the rmap entry for that page early, which means
that functions like folio_mkclean() would end up not serializing with
the page table lock because the page had already been made invisible to
rmap.

And that is a problem, because while the TLB entry exists, we could end
up with the following situation:

 (a) one CPU could come in and clean it, never seeing our mapping of
     the page

 (b) another CPU could continue to use the stale and dirty TLB entry
     and continue to write to said page

resulting in a page that has been dirtied, but then marked clean again,
all while another CPU might have dirtied it some more.

End result: possibly lost dirty data.

This commit uses the same old TLB gather array that we use to delay the
freeing of the page to also say 'remove from rmap after flush', so that
we can keep the rmap entries alive until all TLB entries have been
flushed.

It might be worth noting that this means that the page_zap_pte_rmap() is
now called outside the page table lock. That was never mutual exclusion
(since the same page could be mapped under multiple different page
tables), but it does mean that it needs to use the more careful version
of dec_lruvec_page_state() that doesn't depend on being called in a
non-preemptable context.

NOTE! While the "possibly lost dirty data" sounds catastrophic, for this
all to happen you need to have a user thread doing either madvise() with
MADV_DONTNEED or a full re-mmap() of the area concurrently with another
thread continuing to use said mapping.

So arguably this is about user space doing crazy things, but from a VM
consistency standpoint it's better if we track the dirty bit properly
even when user space goes off the rails.

Reported-by: Nadav Amit <nadav.amit@gmail.com>
Link: https://lore.kernel.org/all/B88D3073-440A-41C7-95F4-895D3F657EF2@gmail.com/
Cc: Will Deacon <will@kernel.org>
Cc: Aneesh Kumar <aneesh.kumar@linux.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Piggin <npiggin@gmail.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com> # s390
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Linus Torvalds
Author Date: 2021-01-21 18:17:25 UTC

tty: fix up iterate_tty_read() EOVERFLOW handling

When I converted the tty_ldisc_ops 'read()' function to take a kernel
pointer, I was a bit too aggressive about the ldisc returning EOVERFLOW.

Yes, we want to have EOVERFLOW override any partially read data (because
the whole point is that the buffer was too small for the whole packet,
and we don't want to see partial packets), but it shouldn't override a
previous EFAULT.

And in fact, it really is just EOVERFLOW that is special and should
throw away any partially read data, not "any error". Admittedly
EOVERFLOW is currently the only one that can happen for a continuation
read - and if the first read iteration returns an error we won't have this issue.

So this is more of a technicality, but let's just make the intent very
explicit, and re-organize the error handling a bit so that this is all
clearer.

Reported-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Greg Kroah-Hartman
Author Date: 2018-09-17 05:24:28 UTC

Merge tag 'linux-kselftest-4.19-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest

Pulled kselftest fixes from Shuah:
 "This Kselftest fixes update for 4.9-rc5 consists of:

  -- fixes to build failures
  -- fixes to add missing config files to increase test coverage
  -- fixes to cgroup test and a new cgroup test for memory.oom.group"

Author: Peter Zijlstra
Author Date: 2018-08-22 15:30:16 UTC

x86/mm: Only use tlb_remove_table() for paravirt

If we don't use paravirt; don't play unnecessary and complicated games
to free page-tables.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Linus Torvalds
Author Date: 2018-05-17 22:17:33 UTC

fs/proc: simplify and clarify get_mm_cmdline() function

We have some very odd semantics for reading the command line through
/proc, because we allow people to rewrite their own command line pretty
much at will, and things get positively funky when you extend your
command line past the point that used to be the end of the command line,
and is now in the environment variable area.

But our weird semantics doesn't mean that we should write weird and
complex code to handle them.

So re-write get_mm_cmdline() to be much simpler, and much more explicit
about what it is actually doing and why. And avoid the extra check for
"is there a NUL character at the end of the command line where I expect
one to be", by simply making the NUL character handling be part of the
normal "once you hit the end of the command line, stop at the first NUL
character" logic.

It's quite possible that we should stop the crazy "walk into
environment" entirely, but happily it's not really the usual case.

NOTE! We tried to really simplify and limit our odd cmdline parsing some
time ago, but people complained. See commit c2c0bb44620d ("proc: fix
PAGE_SIZE limit of /proc/$PID/cmdline") for details about why we have
this complexity.

Cc: Tejun Heo <tj@kernel.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Linus Torvalds
Author Date: 2018-02-27 20:39:30 UTC

Broken, but working, ptregs system call conversion for x86-64

Not-yet-signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Author: Linus Torvalds
Author Date: 2014-06-06 23:35:10 UTC

Merge branch 'akpm' (patches from Andrew Morton) into next

Merge more updates from Andrew Morton:

 - Most of the rest of MM.

   This includes "mark remap_file_pages syscall as deprecated" but the
   actual "replace remap_file_pages syscall with emulation" is held
   back. I guess we'll need to work out when to pull the trigger on
   that one.

 - various minor cleanups to obscure filesystems

 - the drivers/rtc queue

 - hfsplus updates

 - ufs, hpfs, fatfs, affs, reiserfs

 - Documentation/

 - signals

 - procfs

 - cpu hotplug

 - lib/idr.c

 - rapidio

 - sysctl

 - ipc updates

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (171 commits)
  ufs: sb mutex merge + mutex_destroy
  powerpc: update comments for generic idle conversion
  cris: update comments for generic idle conversion
  idle: remove cpu_idle() forward declarations
  nbd: zero from and len fields in NBD_CMD_DISCONNECT.
  mm: convert some level-less printks to pr_*
  MAINTAINERS: adi-buildroot-devel is moderated
  MAINTAINERS: add linux-api for review of API/ABI changes
  mm/kmemleak-test.c: use pr_fmt for logging
  fs/dlm/debug_fs.c: replace seq_printf by seq_puts
  fs/dlm/lockspace.c: convert simple_str to kstr
  fs/dlm/config.c: convert simple_str to kstr
  mm: mark remap_file_pages() syscall as deprecated
  mm: memcontrol: remove unnecessary memcg argument from soft limit functions
  mm: memcontrol: clean up memcg zoneinfo lookup
  mm/memblock.c: call kmemleak directly from memblock_(alloc|free)
  mm/mempool.c: update the kmemleak stack trace for mempool allocations
  lib/radix-tree.c: update the kmemleak stack trace for radix tree allocations
  mm: introduce kmemleak_update_trace()
  mm/kmemleak.c: use %u to print ->checksum
  ...