linux.git/mm/util.c, branch v5.15

mm: fix uninitialized use in overcommit_policy_handler

2021-09-24T23:13:35+00:00

We get an unexpected value of /proc/sys/vm/overcommit_memory after
running the following program:

  int main()
  {
      int fd = open("/proc/sys/vm/overcommit_memory", O_RDWR);
      write(fd, "1", 1);
      write(fd, "2", 1);
      close(fd);
  }

write(fd, "2", 1) will pass *ppos = 1 to proc_dointvec_minmax.
proc_dointvec_minmax will return 0 without setting new_policy.

  t.data = &new_policy;
  ret = proc_dointvec_minmax(&t, write, buffer, lenp, ppos)
      -->do_proc_dointvec
         -->__do_proc_dointvec
              if (write) {
                if (proc_first_pos_non_zero_ignore(ppos, table))
                  goto out;

  sysctl_overcommit_memory = new_policy;

so sysctl_overcommit_memory will be set to an uninitialized value.

Check whether new_policy has been changed by proc_dointvec_minmax.

Link: https://lkml.kernel.org/r/20210923020524.13289-1-chenjun102@huawei.com
Fixes: 56f3547bfa4d ("mm: adjust vm_committed_as_batch according to vm overcommit policy")
Signed-off-by: Chen Jun 
Acked-by: Michal Hocko 
Reviewed-by: Feng Tang 
Reviewed-by: Kefeng Wang 
Cc: Rui Xiang 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: don't allow oversized kvmalloc() calls

2021-09-02T16:47:01+00:00

'kvmalloc()' is a convenience function for people who want to do a
kmalloc() but fall back on vmalloc() if there aren't enough physically
contiguous pages, or if the allocation is larger than what kmalloc()
supports.

However, let's make sure it doesn't get _too_ easy to do crazy things
with it.  In particular, don't allow big allocations that could be due
to integer overflow or underflow.  So make sure the allocation size fits
in an 'int', to protect against trivial integer conversion issues.

Acked-by: Willy Tarreau 
Cc: Kees Cook 
Signed-off-by: Linus Torvalds

mm: Add kvrealloc()

2021-08-09T22:57:43+00:00

During log recovery of an XFS filesystem with 64kB directory
buffers, rebuilding a buffer split across two log records results
in a memory allocation warning from krealloc like this:

xfs filesystem being mounted at /mnt/scratch supports timestamps until 2038 (0x7fffffff)
XFS (dm-0): Unmounting Filesystem
XFS (dm-0): Mounting V5 Filesystem
XFS (dm-0): Starting recovery (logdev: internal)
------------[ cut here ]------------
WARNING: CPU: 5 PID: 3435170 at mm/page_alloc.c:3539 get_page_from_freelist+0xdee/0xe40
.....
RIP: 0010:get_page_from_freelist+0xdee/0xe40
Call Trace:
 ? complete+0x3f/0x50
 __alloc_pages+0x16f/0x300
 alloc_pages+0x87/0x110
 kmalloc_order+0x2c/0x90
 kmalloc_order_trace+0x1d/0x90
 __kmalloc_track_caller+0x215/0x270
 ? xlog_recover_add_to_cont_trans+0x63/0x1f0
 krealloc+0x54/0xb0
 xlog_recover_add_to_cont_trans+0x63/0x1f0
 xlog_recovery_process_trans+0xc1/0xd0
 xlog_recover_process_ophdr+0x86/0x130
 xlog_recover_process_data+0x9f/0x160
 xlog_recover_process+0xa2/0x120
 xlog_do_recovery_pass+0x40b/0x7d0
 ? __irq_work_queue_local+0x4f/0x60
 ? irq_work_queue+0x3a/0x50
 xlog_do_log_recovery+0x70/0x150
 xlog_do_recover+0x38/0x1d0
 xlog_recover+0xd8/0x170
 xfs_log_mount+0x181/0x300
 xfs_mountfs+0x4a1/0x9b0
 xfs_fs_fill_super+0x3c0/0x7b0
 get_tree_bdev+0x171/0x270
 ? suffix_kstrtoint.constprop.0+0xf0/0xf0
 xfs_fs_get_tree+0x15/0x20
 vfs_get_tree+0x24/0xc0
 path_mount+0x2f5/0xaf0
 __x64_sys_mount+0x108/0x140
 do_syscall_64+0x3a/0x70
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Essentially, we are taking a multi-order allocation from kmem_alloc()
(which has an open coded no fail, no warn loop) and then
reallocating it out to 64kB using krealloc(__GFP_NOFAIL) and that is
then triggering the above warning.

This is a regression caused by converting this code from an open
coded no fail/no warn reallocation loop to using __GFP_NOFAIL.

What we actually need here is kvrealloc(), so that if contiguous
page allocation fails we fall back to vmalloc() and we don't
get nasty warnings happening in XFS.

Fixes: 771915c4f688 ("xfs: remove kmem_realloc()")
Signed-off-by: Dave Chinner 
Acked-by: Mel Gorman 
Reviewed-by: Darrick J. Wong 
Signed-off-by: Darrick J. Wong

mm: Make copy_huge_page() always available

2021-07-12T18:30:56+00:00

Rewrite copy_huge_page() and move it into mm/util.c so it's always
available.  Fixes an exposure of uninitialised memory on configurations
with HUGETLB and UFFD enabled and MIGRATION disabled.

Fixes: 8cc5fcbb5be8 ("mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY")
Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Mike Kravetz 
Signed-off-by: Linus Torvalds

Merge branch 'core-rcu-2021.07.04' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

2021-07-04T19:58:33+00:00

Pull RCU updates from Paul McKenney:

 - Bitmap parsing support for "all" as an alias for all bits

 - Documentation updates

 - Miscellaneous fixes, including some that overlap into mm and lockdep

 - kvfree_rcu() updates

 - mem_dump_obj() updates, with acks from one of the slab-allocator
   maintainers

 - RCU NOCB CPU updates, including limited deoffloading

 - SRCU updates

 - Tasks-RCU updates

 - Torture-test updates

* 'core-rcu-2021.07.04' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (78 commits)
  tasks-rcu: Make show_rcu_tasks_gp_kthreads() be static inline
  rcu-tasks: Make ksoftirqd provide RCU Tasks quiescent states
  rcu: Add missing __releases() annotation
  rcu: Remove obsolete rcu_read_unlock() deadlock commentary
  rcu: Improve comments describing RCU read-side critical sections
  rcu: Create an unrcu_pointer() to remove __rcu from a pointer
  srcu: Early test SRCU polling start
  rcu: Fix various typos in comments
  rcu/nocb: Unify timers
  rcu/nocb: Prepare for fine-grained deferred wakeup
  rcu/nocb: Only cancel nocb timer if not polling
  rcu/nocb: Delete bypass_timer upon nocb_gp wakeup
  rcu/nocb: Cancel nocb_timer upon nocb_gp wakeup
  rcu/nocb: Allow de-offloading rdp leader
  rcu/nocb: Directly call __wake_nocb_gp() from bypass timer
  rcu: Don't penalize priority boosting when there is nothing to boost
  rcu: Point to documentation of ordering guarantees
  rcu: Make rcu_gp_cleanup() be noinline for tracing
  rcu: Restrict RCU_STRICT_GRACE_PERIOD to at most four CPUs
  rcu: Make show_rcu_gp_kthreads() dump rcu_node structures blocking GP
  ...

mm: introduce page_offline_(begin|end|freeze|thaw) to synchronize setting PageOffline()

2021-07-01T03:47:28+00:00

A driver might set a page logically offline -- PageOffline() -- and turn
the page inaccessible in the hypervisor; after that, access to page
content can be fatal.  One example is virtio-mem; while unplugged memory
-- marked as PageOffline() can currently be read in the hypervisor, this
will no longer be the case in the future; for example, when having a
virtio-mem device backed by huge pages in the hypervisor.

Some special PFN walkers -- i.e., /proc/kcore -- read content of random
pages after checking PageOffline(); however, these PFN walkers can race
with drivers that set PageOffline().

Let's introduce page_offline_(begin|end|freeze|thaw) for synchronizing.

page_offline_freeze()/page_offline_thaw() allows for a subsystem to
synchronize with such drivers, achieving that a page cannot be set
PageOffline() while frozen.

page_offline_begin()/page_offline_end() is used by drivers that care about
such races when setting a page PageOffline().

For simplicity, use a rwsem for now; neither drivers nor users are
performance sensitive.

Link: https://lkml.kernel.org/r/20210526093041.8800-5-david@redhat.com
Signed-off-by: David Hildenbrand 
Acked-by: Michal Hocko 
Reviewed-by: Mike Rapoport 
Reviewed-by: Oscar Salvador 
Cc: Aili Yao 
Cc: Alexey Dobriyan 
Cc: Alex Shi 
Cc: Haiyang Zhang 
Cc: Jason Wang 
Cc: Jiri Bohac 
Cc: "K. Y. Srinivasan" 
Cc: "Matthew Wilcox (Oracle)" 
Cc: "Michael S. Tsirkin" 
Cc: Mike Kravetz 
Cc: Naoya Horiguchi 
Cc: Roman Gushchin 
Cc: Stephen Hemminger 
Cc: Steven Price 
Cc: Wei Liu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/slub: Add Support for free path information of an object

2021-05-10T23:01:41+00:00

This commit adds enables a stack dump for the last free of an object:

slab kmalloc-64 start c8ab0140 data offset 64 pointer offset 0 size 64 allocated at meminfo_proc_show+0x40/0x4fc
[   20.192078]     meminfo_proc_show+0x40/0x4fc
[   20.192263]     seq_read_iter+0x18c/0x4c4
[   20.192430]     proc_reg_read_iter+0x84/0xac
[   20.192617]     generic_file_splice_read+0xe8/0x17c
[   20.192816]     splice_direct_to_actor+0xb8/0x290
[   20.193008]     do_splice_direct+0xa0/0xe0
[   20.193185]     do_sendfile+0x2d0/0x438
[   20.193345]     sys_sendfile64+0x12c/0x140
[   20.193523]     ret_fast_syscall+0x0/0x58
[   20.193695]     0xbeeacde4
[   20.193822]  Free path:
[   20.193935]     meminfo_proc_show+0x5c/0x4fc
[   20.194115]     seq_read_iter+0x18c/0x4c4
[   20.194285]     proc_reg_read_iter+0x84/0xac
[   20.194475]     generic_file_splice_read+0xe8/0x17c
[   20.194685]     splice_direct_to_actor+0xb8/0x290
[   20.194870]     do_splice_direct+0xa0/0xe0
[   20.195014]     do_sendfile+0x2d0/0x438
[   20.195174]     sys_sendfile64+0x12c/0x140
[   20.195336]     ret_fast_syscall+0x0/0x58
[   20.195491]     0xbeeacde4

Acked-by: Vlastimil Babka 
Co-developed-by: Vaneet Narang 
Signed-off-by: Vaneet Narang 
Signed-off-by: Maninder Singh 
Signed-off-by: Paul E. McKenney

mm/util.c: fix typo

2021-05-05T18:27:25+00:00

s/condtion/condition/

Link: https://lkml.kernel.org/r/20210317033439.3429411-1-unixbhaskar@gmail.com
Signed-off-by: Bhaskar Chowdhury 
Acked-by: Randy Dunlap 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/util.c: reduce mem_dump_obj() object size

2021-05-05T18:27:25+00:00

Simplify the code by using a temporary and reduce the object size by
using a single call to pr_cont().  Reverse a test and unindent a block
too.

$ size mm/util.o* (defconfig x86-64)
   text	   data	    bss	    dec	    hex	filename
   7419	    372	     40	   7831	   1e97	mm/util.o.new
   7477	    372	     40	   7889	   1ed1	mm/util.o.old

Link: https://lkml.kernel.org/r/a6e105886338f68afd35f7a13d73bcf06b0cc732.camel@perches.com
Signed-off-by: Joe Perches 
Reviewed-by: Andrew Morton 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: move page_mapping_file to pagemap.h

2021-04-30T18:20:37+00:00

page_mapping_file() is only used by some architectures, and then it
is usually only used in one place.  Make it a static inline function
so other architectures don't have to carry this dead code.

Link: https://lkml.kernel.org/r/20210317123011.350118-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: David Hildenbrand 
Acked-by: Mike Rapoport 
Cc: Huang Ying 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds