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Jason A. Donenfeld f5ad508340 mm: do not BUG_ON missing brk mapping, because userspace can unmap it 
The following program will trigger the BUG_ON that this patch removes,
because the user can munmap() mm->brk:

  #include <sys/syscall.h>
  #include <sys/mman.h>
  #include <assert.h>
  #include <unistd.h>

  static void *brk_now(void)
  {
    return (void *)syscall(SYS_brk, 0);
  }

  static void brk_set(void *b)
  {
    assert(syscall(SYS_brk, b) != -1);
  }

  int main(int argc, char *argv[])
  {
    void *b = brk_now();
    brk_set(b + 4096);
    assert(munmap(b - 4096, 4096 * 2) == 0);
    brk_set(b);
    return 0;
  }

Compile that with musl, since glibc actually uses brk(), and then
execute it, and it'll hit this splat:

  kernel BUG at mm/mmap.c:229!
  invalid opcode: 0000 [#1] PREEMPT SMP
  CPU: 12 PID: 1379 Comm: a.out Tainted: G S   U             6.1.0-rc7+ #419
  RIP: 0010:__do_sys_brk+0x2fc/0x340
  Code: 00 00 4c 89 ef e8 04 d3 fe ff eb 9a be 01 00 00 00 4c 89 ff e8 35 e0 fe ff e9 6e ff ff ff 4d 89 a7 20>
  RSP: 0018:ffff888140bc7eb0 EFLAGS: 00010246
  RAX: 0000000000000000 RBX: 00000000007e7000 RCX: ffff8881020fe000
  RDX: ffff8881020fe001 RSI: ffff8881955c9b00 RDI: ffff8881955c9b08
  RBP: 0000000000000000 R08: ffff8881955c9b00 R09: 00007ffc77844000
  R10: 0000000000000000 R11: 0000000000000001 R12: 00000000007e8000
  R13: 00000000007e8000 R14: 00000000007e7000 R15: ffff8881020fe000
  FS:  0000000000604298(0000) GS:ffff88901f700000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000603fe0 CR3: 000000015ba9a005 CR4: 0000000000770ee0
  PKRU: 55555554
  Call Trace:
   <TASK>
   do_syscall_64+0x2b/0x50
   entry_SYSCALL_64_after_hwframe+0x46/0xb0
  RIP: 0033:0x400678
  Code: 10 4c 8d 41 08 4c 89 44 24 10 4c 8b 01 8b 4c 24 08 83 f9 2f 77 0a 4c 8d 4c 24 20 4c 01 c9 eb 05 48 8b>
  RSP: 002b:00007ffc77863890 EFLAGS: 00000212 ORIG_RAX: 000000000000000c
  RAX: ffffffffffffffda RBX: 000000000040031b RCX: 0000000000400678
  RDX: 00000000004006a1 RSI: 00000000007e6000 RDI: 00000000007e7000
  RBP: 00007ffc77863900 R08: 0000000000000000 R09: 00000000007e6000
  R10: 00007ffc77863930 R11: 0000000000000212 R12: 00007ffc77863978
  R13: 00007ffc77863988 R14: 0000000000000000 R15: 0000000000000000
   </TASK>

Instead, just return the old brk value if the original mapping has been
removed.

[akpm@linux-foundation.org: fix changelog, per Liam]
Link: https://lkml.kernel.org/r/20221202162724.2009-1-Jason@zx2c4.com
Fixes: 2e7ce7d354f2 ("mm/mmap: change do_brk_flags() to expand existing VMA and add do_brk_munmap()")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Jann Horn <jannh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-12-09 18:41:16 -08:00
..
damon
mm/damon/sysfs: fix wrong empty schemes assumption under online tuning in damon_sysfs_set_schemes()
2022-11-30 14:49:41 -08:00
kasan
Random number generator fixes for Linux 6.1-rc1.
2022-10-16 15:27:07 -07:00
kfence
kfence: fix stack trace pruning
2022-11-22 18:50:44 -08:00
kmsan
kmsan: core: kmsan_in_runtime() should return true in NMI context
2022-11-08 15:57:24 -08:00
backing-dev.c
mm: backing-dev: Remove the unneeded result variable
2022-09-11 20:26:02 -07:00
balloon_compaction.c
mm: Convert all PageMovable users to movable_operations
2022-08-02 12:34:03 -04:00
bootmem_info.c
bootmem: remove the vmemmap pages from kmemleak in put_page_bootmem
2022-08-28 14:02:45 -07:00
cma_debug.c
mm/cma_debug: show complete cma name in debugfs directories
2022-09-11 20:25:50 -07:00
cma_sysfs.c
…
cma.c
Revert "mm/cma.c: remove redundant cma_mutex lock"
2022-05-13 15:11:26 -07:00
cma.h
mm/cma: provide option to opt out from exposing pages on activation failure
2022-03-22 15:57:09 -07:00
compaction.c
mm: migrate: fix THP's mapcount on isolation
2022-11-30 14:49:41 -08:00
debug_page_ref.c
…
debug_vm_pgtable.c
docs: rename Documentation/vm to Documentation/mm
2022-06-27 12:52:53 -07:00
debug.c
mm: remove the vma linked list
2022-09-26 19:46:26 -07:00
dmapool.c
mm/dmapool.c: revert "make dma pool to use kmalloc_node"
2022-01-15 16:30:28 +02:00
early_ioremap.c
mm/early_ioremap: declare early_memremap_pgprot_adjust()
2022-03-22 15:57:11 -07:00
fadvise.c
riscv: compat: syscall: Add compat_sys_call_table implementation
2022-04-26 13:36:25 -07:00
failslab.c
mm: fix unexpected changes to {failslab|fail_page_alloc}.attr
2022-11-22 18:50:44 -08:00
filemap.c
- Yu Zhao's Multi-Gen LRU patches are here. They've been under test in
2022-10-10 17:53:04 -07:00
folio-compat.c
mm: remove try_to_free_swap()
2022-10-03 14:02:53 -07:00
frontswap.c
frontswap: don't call ->init if no ops are registered
2022-09-26 12:14:34 -07:00
gup_test.c
mm: rename is_pinnable_page() to is_longterm_pinnable_page()
2022-07-17 17:14:27 -07:00
gup_test.h
…
gup.c
Five hotfixes - three for nilfs2, two for MM. For are cc:stable, one is
2022-10-12 11:16:58 -07:00
highmem.c
highmem: fix kmap_to_page() for kmap_local_page() addresses
2022-10-12 18:51:51 -07:00
hmm.c
mm/swap: add swp_offset_pfn() to fetch PFN from swap entry
2022-09-26 19:46:05 -07:00
huge_memory.c
Partly revert "mm/thp: carry over dirty bit when thp splits on pmd"
2022-11-08 15:57:23 -08:00
hugetlb_cgroup.c
hugetlb_cgroup: use helper for_each_hstate and hstate_index
2022-09-11 20:25:53 -07:00
hugetlb_vmemmap.c
mm: hugetlb_vmemmap: include missing linux/moduleparam.h
2022-11-08 15:57:23 -08:00
hugetlb_vmemmap.h
mm: hugetlb_vmemmap: improve hugetlb_vmemmap code readability
2022-08-08 18:06:43 -07:00
hugetlb.c
hugetlb: don't delete vma_lock in hugetlb MADV_DONTNEED processing
2022-11-30 14:49:40 -08:00
hwpoison-inject.c
mm/hwpoison: add __init/__exit annotations to module init/exit funcs
2022-10-03 14:03:05 -07:00
init-mm.c
mm: remove rb tree.
2022-09-26 19:46:16 -07:00
internal.h
mm/page_alloc: make boot_nodestats static
2022-10-03 14:03:30 -07:00
interval_tree.c
…
io-mapping.c
…
ioremap.c
mm: ioremap: Add ioremap/iounmap_allowed()
2022-06-27 12:22:31 +01:00
Kconfig
- Yu Zhao's Multi-Gen LRU patches are here. They've been under test in
2022-10-10 17:53:04 -07:00
Kconfig.debug
Two followon fixes for the post-5.19 series "Use pageblock_order for cma
2022-05-27 11:40:49 -07:00
khugepaged.c
mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths
2022-11-30 14:49:42 -08:00
kmemleak.c
mm/kmemleak: prevent soft lockup in kmemleak_scan()'s object iteration loops
2022-10-28 13:37:22 -07:00
ksm.c
ksm: use a folio in replace_page()
2022-10-03 14:02:53 -07:00
list_lru.c
mm: kmem: make mem_cgroup_from_obj() vmalloc()-safe
2022-06-16 19:48:31 -07:00
maccess.c
asm-generic updates for 5.18
2022-03-23 18:03:08 -07:00
madvise.c
madvise: use zap_page_range_single for madvise dontneed
2022-11-30 14:49:40 -08:00
Makefile
mm: memcontrol: drop dead CONFIG_MEMCG_SWAP config symbol
2022-10-03 14:03:36 -07:00
mapping_dirty_helpers.c
mm: move tlb_flush_pending inline helpers to mm_inline.h
2022-01-15 16:30:27 +02:00
memblock.c
mm: add pageblock_align() macro
2022-10-03 14:03:04 -07:00
memcontrol.c
mm: correctly charge compressed memory to its memcg
2022-11-22 18:50:42 -08:00
memfd.c
memfd: fix F_SEAL_WRITE after shmem huge page allocated
2022-03-05 11:08:32 -08:00
memory_hotplug.c
mm: add pageblock_aligned() macro
2022-10-03 14:03:04 -07:00
memory-failure.c
hugetlbfs: don't delete error page from pagecache
2022-11-08 15:57:22 -08:00
memory-tiers.c
memory tier, sysfs: rename attribute "nodes" to "nodelist"
2022-10-28 13:37:22 -07:00
memory.c
hugetlb: don't delete vma_lock in hugetlb MADV_DONTNEED processing
2022-11-30 14:49:40 -08:00
mempolicy.c
mm/mempolicy: fix mbind_range() arguments to vma_merge()
2022-10-20 21:27:21 -07:00
mempool.c
mm/mempool: use might_alloc()
2022-06-16 19:48:30 -07:00
memremap.c
mm/memremap.c: map FS_DAX device memory as decrypted
2022-11-08 15:57:23 -08:00
memtest.c
…
migrate_device.c
mm/migrate_device: return number of migrating pages in args->cpages
2022-11-22 18:50:43 -08:00
migrate.c
mm: migrate: fix return value if all subpages of THPs are migrated successfully
2022-10-28 13:37:22 -07:00
mincore.c
mm: teach core mm about pte markers
2022-05-13 07:20:09 -07:00
mlock.c
mm/mlock: drop dead code in count_mm_mlocked_page_nr()
2022-09-26 19:46:27 -07:00
mm_init.c
mm: multi-gen LRU: groundwork
2022-09-26 19:46:09 -07:00
mm_slot.h
mm: introduce common struct mm_slot
2022-10-03 14:02:43 -07:00
mmap_lock.c
…
mmap.c
mm: do not BUG_ON missing brk mapping, because userspace can unmap it
2022-12-09 18:41:16 -08:00
mmu_gather.c
mm/khugepaged: fix GUP-fast interaction by sending IPI
2022-11-30 14:49:42 -08:00
mmu_notifier.c
mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove()
2022-04-21 20:01:10 -07:00
mmzone.c
mm: multi-gen LRU: groundwork
2022-09-26 19:46:09 -07:00
mprotect.c
mm/uffd: fix warning without PTE_MARKER_UFFD_WP compiled in
2022-10-12 15:56:46 -07:00
mremap.c
mm: add merging after mremap resize
2022-09-26 19:46:28 -07:00
msync.c
mm/msync: use vma_find() instead of vma linked list
2022-09-26 19:46:25 -07:00
nommu.c
mm: remove the vma linked list
2022-09-26 19:46:26 -07:00
oom_kill.c
mm: reduce noise in show_mem for lowmem allocations
2022-09-26 19:46:29 -07:00
page_alloc.c
mm: fix unexpected changes to {failslab|fail_page_alloc}.attr
2022-11-22 18:50:44 -08:00
page_counter.c
mm: page_counter: remove unneeded atomic ops for low/min
2022-09-11 20:26:01 -07:00
page_ext.c
mm/page_exit: fix kernel doc warning in page_ext_put()
2022-11-22 18:50:41 -08:00
page_idle.c
mm: don't be stuck to rmap lock on reclaim path
2022-05-19 14:08:54 -07:00
page_io.c
swap: convert swap_writepage() to use a folio
2022-10-03 14:02:52 -07:00
page_isolation.c
mm/page_isolation: fix clang deadcode warning
2022-10-28 13:37:22 -07:00
page_owner.c
mm: reuse pageblock_start/end_pfn() macro
2022-10-03 14:03:03 -07:00
page_poison.c
…
page_reporting.c
…
page_reporting.h
…
page_table_check.c
mm/page_table_check: fix typos
2022-10-03 14:03:27 -07:00
page_vma_mapped.c
mm/swap: add swp_offset_pfn() to fetch PFN from swap entry
2022-09-26 19:46:05 -07:00
page-writeback.c
mm: export balance_dirty_pages_ratelimited_flags()
2022-09-26 12:28:07 +02:00
pagewalk.c
- Yu Zhao's Multi-Gen LRU patches are here. They've been under test in
2022-10-10 17:53:04 -07:00
percpu-internal.h
percpu: improve percpu_alloc_percpu event trace
2022-05-13 07:20:18 -07:00
percpu-km.c
…
percpu-stats.c
mm: use vmalloc_array and vcalloc for array allocations
2022-03-08 09:30:46 -05:00
percpu-vm.c
…
percpu.c
mm: percpu: use kmemleak_ignore_phys() instead of kmemleak_free()
2022-07-17 17:14:47 -07:00
pgalloc-track.h
…
pgtable-generic.c
mm: avoid unnecessary flush on change_huge_pmd()
2022-05-13 07:20:05 -07:00
process_vm_access.c
…
ptdump.c
mm: pagewalk: Fix race between unmap and page walker
2022-09-03 10:13:13 -07:00
readahead.c
mm: add PSI accounting around ->read_folio and ->readahead calls
2022-09-20 08:24:38 -06:00
rmap.c
- Yu Zhao's Multi-Gen LRU patches are here. They've been under test in
2022-10-10 17:53:04 -07:00
rodata_test.c
mm/rodata_test: use PAGE_ALIGNED() helper
2022-10-03 14:03:05 -07:00
secretmem.c
mm/secretmem: remove reduntant return value
2022-10-03 14:03:36 -07:00
shmem.c
mm/shmem: ensure proper fallback if page faults
2022-10-28 13:37:23 -07:00
shrinker_debug.c
mm: shrinkers: fix double kfree on shrinker name
2022-07-29 18:07:13 -07:00
shuffle.c
mm/shuffle: convert module_param_call to module_param_cb
2022-10-03 14:03:07 -07:00
shuffle.h
…
slab_common.c
- Yu Zhao's Multi-Gen LRU patches are here. They've been under test in
2022-10-10 17:53:04 -07:00
slab.c
Random number generator fixes for Linux 6.1-rc1.
2022-10-16 15:27:07 -07:00
slab.h
- Yu Zhao's Multi-Gen LRU patches are here. They've been under test in
2022-10-10 17:53:04 -07:00
slob.c
Merge branch 'slab/for-6.1/kmalloc_size_roundup' into slab/for-next
2022-09-29 11:30:55 +02:00
slub.c
treewide: use prandom_u32_max() when possible, part 1
2022-10-11 17:42:55 -06:00
sparse-vmemmap.c
mm: hugetlb_vmemmap: move vmemmap code related to HugeTLB to hugetlb_vmemmap.c
2022-08-08 18:06:42 -07:00
sparse.c
mm: memory_hotplug: enumerate all supported section flags
2022-07-03 18:08:49 -07:00
swap_cgroup.c
mm: memcontrol: don't allocate cgroup swap arrays when memcg is disabled
2022-10-03 14:03:36 -07:00
swap_slots.c
mm/swap: convert put_swap_page() to put_swap_folio()
2022-10-03 14:02:46 -07:00
swap_state.c
swap_state: convert free_swap_cache() to use a folio
2022-10-03 14:02:51 -07:00
swap.c
mm: add folio_add_lru_vma()
2022-10-03 14:02:45 -07:00
swap.h
mm: remove lookup_swap_cache()
2022-10-03 14:02:51 -07:00
swapfile.c
swapfile: fix soft lockup in scan_swap_map_slots
2022-11-22 18:50:44 -08:00
truncate.c
mm: add split_folio()
2022-10-03 14:02:45 -07:00
usercopy.c
usercopy: use unsigned long instead of uintptr_t
2022-07-01 17:03:38 -07:00
userfaultfd.c
mm/shmem: use page_mapping() to detect page cache for uffd continue
2022-11-08 15:57:23 -08:00
util.c
- Yu Zhao's Multi-Gen LRU patches are here. They've been under test in
2022-10-10 17:53:04 -07:00
vmalloc.c
mm: kmsan: maintain KMSAN metadata for page operations
2022-10-03 14:03:20 -07:00
vmpressure.c
mm/vmpressure: fix data-race with memcg->socket_pressure
2021-11-06 13:30:40 -07:00
vmscan.c
mm: introduce arch_has_hw_nonleaf_pmd_young()
2022-11-30 14:49:41 -08:00
vmstat.c
- Yu Zhao's Multi-Gen LRU patches are here. They've been under test in
2022-10-10 17:53:04 -07:00
workingset.c
mm: multi-gen LRU: minimal implementation
2022-09-26 19:46:09 -07:00
z3fold.c
mm: Convert all PageMovable users to movable_operations
2022-08-02 12:34:03 -04:00
zbud.c
…
zpool.c
zpool: remove the list of pools_head
2022-01-15 16:30:31 +02:00
zsmalloc.c
zsmalloc: zs_destroy_pool: add size_class NULL check
2022-10-20 21:27:21 -07:00
zswap.c
mm/swap: remove the end_write_func argument to __swap_writepage
2022-09-11 20:25:50 -07:00