We found a nullptr in __mod_lruvec_page_state(),
UIO driver:
kmalloc(PAGE_SIZE)
UIO user:
mmap() then read, but before user read the page, others may alloc the
page that belong to the same compound page and modify the head page's obj_cgroups
likes that:
[ 94.845687] memcg_alloc_page_obj_cgroups+0x50/0xa0
[ 94.846334] slab_post_alloc_hook+0xc8/0x184
[ 94.846852] kmem_cache_alloc+0x148/0x2a4
[ 94.847346] __d_alloc+0x30/0x2e4
[ 94.847809] d_alloc+0x30/0xc0
Then when the user reads the page, in __mod_lruvec_page_state(), it will get the
nullptr in head->mem_cgroup.
[ 94.882699] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000080
[ 94.882773] Mem abort info:
[ 94.882819] ESR = 0x96000006
[ 94.882953] EC = 0x25: DABT (current EL), IL = 32 bits
[ 94.883000] SET = 0, FnV = 0
[ 94.883043] EA = 0, S1PTW = 0
[ 94.883089] Data abort info:
[ 94.883134] ISV = 0, ISS = 0x00000006
[ 94.883179] CM = 0, WnR = 0
[ 94.883402] user pgtable: 4k pages, 48-bit VAs, pgdp=000000010c355000
[ 94.883495] [0000000000000080] pgd=000000010c046003, p4d=000000010c046003, pud=000000010c368003, pmd=0000000000000000
[ 94.884225] Internal error: Oops: 96000006 [#1] PREEMPT SMP
[ 94.884480] Modules linked in:
[ 94.884788] CPU: 0 PID: 250 Comm: uio_user_mmap Tainted: G B 5.10.0-07799-ged92fcf8d408-dirty #112
[ 94.884837] Hardware name: linux,dummy-virt (DT)
[ 94.885052] pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--)
[ 94.885169] pc : __mod_lruvec_page_state+0x118/0x180
[ 94.885249] lr : __mod_lruvec_page_state+0x118/0x180
[ 94.885297] sp : ffff2872ce25fb40
[ 94.885402] x29: ffff2872ce25fb40 x28: 0000000000000254
[ 94.885572] x27: 0000000000000000 x26: ffff2872fe2d7c38
[ 94.885724] x25: ffffa000242e7dc0 x24: 0000000000000001
[ 94.885872] x23: 0000000000000012 x22: ffffa00022bcfc60
[ 94.886030] x21: ffff2872fffeb380 x20: 0000000000000144
[ 94.886169] x19: 0000000000000000 x18: 0000000000000000
[ 94.886331] x17: 0000000000000000 x16: 0000000000000000
[ 94.886476] x15: 0000000000000000 x14: 3078303a7865646e
[ 94.886625] x13: 6920303030303030 x12: 1fffe50e5b713f20
[ 94.886765] x11: ffff850e5b713f20 x10: 616d20303a746e75
[ 94.886947] x9 : dfffa00000000000 x8 : 3266666666203d20
[ 94.887095] x7 : ffff2872db89f903 x6 : 0000000000000000
[ 94.887236] x5 : 0000000000000000 x4 : dfffa00000000000
[ 94.887381] x3 : ffffa00021e6c5dc x2 : 0000000000000000
[ 94.887515] x1 : 0000000000000008 x0 : 0000000000000000
[ 94.887702] Call trace:
[ 94.887840] __mod_lruvec_page_state+0x118/0x180
[ 94.887919] page_add_file_rmap+0xa8/0xe0
[ 94.887998] alloc_set_pte+0x2c4/0x2d0
[ 94.888074] finish_fault+0x94/0xcc
[ 94.888157] handle_mm_fault+0x7c8/0x1094
[ 94.888230] do_page_fault+0x358/0x490
[ 94.888300] do_translation_fault+0x38/0x54
[ 94.888370] do_mem_abort+0x5c/0xe4
[ 94.888435] el0_da+0x3c/0x4c
[ 94.888506] el0_sync_handler+0xd8/0x14c
[ 94.888573] el0_sync+0x148/0x180
[ 94.888963] Code: d2835101 8b0102b3 91020260 9400e8da (f9404260)
[ 94.889860] ---[ end trace 1de53a0bd9084cde ]---
[ 94.890244] Kernel panic - not syncing: Oops: Fatal exception
[ 94.890620] SMP: stopping secondary CPUs
[ 94.891117] Kernel Offset: 0x11c00000 from 0xffffa00010000000
[ 94.891179] PHYS_OFFSET: 0xffffd78e40000000
[ 94.891293] CPU features: 0x0660012,41002000
[ 94.891365] Memory Limit: none
[ 94.927552] ---[ end Kernel panic - not syncing: Oops: Fatal exception ]---
1. Roman Gushchin's 4 patch remove this limitation by moving the PageKmemcg
flag into one of the free bits of the page->mem_cgroup pointer. Also it
formalizes accesses to the page->mem_cgroup and page->obj_cgroups
using new helpers, adds several checks and removes a couple of obsolete
functions.
Link: https://lkml.kernel.org/r/20201027001657.3398190-1-guro@xxxxxx
2. Muchun Song's patchset aim to make those kmem pages to drop the reference
to memory cgroup by using the APIs of obj_cgroup.
Link: https://lkml.kernel.org/r/20210319163821.20704-1-songmuchun@xxxxxxxxxxxxx
3. Wang Hai's patch is a bugfix for "mm: memcontrol/slab: Use helpers to
access slab page's memcg_data"
Link: https://lkml.kernel.org/r/20210728145655.274476-1-wanghai38@xxxxxxxxxx
Muchun Song (6):
mm: memcontrol: introduce obj_cgroup_{un}charge_pages
mm: memcontrol: directly access page->memcg_data in mm/page_alloc.c
mm: memcontrol: change ug->dummy_page only if memcg changed
mm: memcontrol: use obj_cgroup APIs to charge kmem pages
Conflict for commit c47d5032ed3002311a4188eae51f4641ec436beb not merged
mm: memcontrol: inline __memcg_kmem_{un}charge() into
obj_cgroup_{un}charge_pages()
mm: memcontrol: move PageMemcgKmem to the scope of CONFIG_MEMCG_KMEM
Roman Gushchin (4):
mm: memcontrol: Use helpers to read page's memcg data
Conflict function:split_page_memcg(), for commit 002ea848d7fd3bdcb6281e75bdde28095c2cd549
mm: memcontrol/slab: Use helpers to access slab page's memcg_data
mm: Introduce page memcg flags
mm: Convert page kmemcg type to a page memcg flag
Wang Hai (1):
mm/memcg: fix NULL pointer dereference in memcg_slab_free_hook()
fs/buffer.c | 2 +-
fs/iomap/buffered-io.c | 2 +-
include/linux/memcontrol.h | 320 +++++++++++++++++++++++++++--
include/linux/mm.h | 22 --
include/linux/mm_types.h | 5 +-
include/linux/page-flags.h | 11 +-
include/trace/events/writeback.h | 2 +-
kernel/fork.c | 7 +-
mm/debug.c | 4 +-
mm/huge_memory.c | 4 +-
mm/memcontrol.c | 336 +++++++++++++++----------------
mm/page_alloc.c | 8 +-
mm/page_io.c | 6 +-
mm/slab.h | 38 +---
mm/workingset.c | 2 +-
15 files changed, 493 insertions(+), 276 deletions(-)
--
2.18.0.huawei.25
