Re: [PATCHv2 2/2] efi: apply memblock cap after memblock_add()

[Pingfan Liu <kernelfans@gmail.com>]

On Tue, Dec 14, 2021 at 08:55:18AM -0600, Rob Herring wrote:
> On Mon, Dec 13, 2021 at 10:02 PM Pingfan Liu <kernelfans@gmail.com> wrote:
> >
> > On arm64, during kdump kernel saves vmcore, it runs into the following bug:
> > ...
> > [   15.148919] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmem_cache_node' (offset 0, size 4096)!
> > [   15.159707] ------------[ cut here ]------------
> > [   15.164311] kernel BUG at mm/usercopy.c:99!
> > [   15.168482] Internal error: Oops - BUG: 0 [#1] SMP
> > [   15.173261] Modules linked in: xfs libcrc32c crct10dif_ce ghash_ce sha2_ce sha256_arm64 sha1_ce sbsa_gwdt ast i2c_algo_bit drm_vram_helper drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cec drm_ttm_helper ttm drm nvme nvme_core xgene_hwmon i2c_designware_platform i2c_designware_core dm_mirror dm_region_hash dm_log dm_mod overlay squashfs zstd_decompress loop
> > [   15.206186] CPU: 0 PID: 542 Comm: cp Not tainted 5.16.0-rc4 #1
> > [   15.212006] Hardware name: GIGABYTE R272-P30-JG/MP32-AR0-JG, BIOS F12 (SCP: 1.5.20210426) 05/13/2021
> > [   15.221125] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > [   15.228073] pc : usercopy_abort+0x9c/0xa0
> > [   15.232074] lr : usercopy_abort+0x9c/0xa0
> > [   15.236070] sp : ffff8000121abba0
> > [   15.239371] x29: ffff8000121abbb0 x28: 0000000000003000 x27: 0000000000000000
> > [   15.246494] x26: 0000000080000400 x25: 0000ffff885c7000 x24: 0000000000000000
> > [   15.253617] x23: 000007ff80400000 x22: ffff07ff80401000 x21: 0000000000000001
> > [   15.260739] x20: 0000000000001000 x19: ffff07ff80400000 x18: ffffffffffffffff
> > [   15.267861] x17: 656a626f2042554c x16: 53206d6f72662064 x15: 6574636574656420
> > [   15.274983] x14: 74706d6574746120 x13: 2129363930342065 x12: 7a6973202c302074
> > [   15.282105] x11: ffffc8b041d1b148 x10: 00000000ffff8000 x9 : ffffc8b04012812c
> > [   15.289228] x8 : 00000000ffff7fff x7 : ffffc8b041d1b148 x6 : 0000000000000000
> > [   15.296349] x5 : 0000000000000000 x4 : 0000000000007fff x3 : 0000000000000000
> > [   15.303471] x2 : 0000000000000000 x1 : ffff07ff8c064800 x0 : 000000000000006b
> > [   15.310593] Call trace:
> > [   15.313027]  usercopy_abort+0x9c/0xa0
> > [   15.316677]  __check_heap_object+0xd4/0xf0
> > [   15.320762]  __check_object_size.part.0+0x160/0x1e0
> > [   15.325628]  __check_object_size+0x2c/0x40
> > [   15.329711]  copy_oldmem_page+0x7c/0x140
> > [   15.333623]  read_from_oldmem.part.0+0xfc/0x1c0
> > [   15.338142]  __read_vmcore.constprop.0+0x23c/0x350
> > [   15.342920]  read_vmcore+0x28/0x34
> > [   15.346309]  proc_reg_read+0xb4/0xf0
> > [   15.349871]  vfs_read+0xb8/0x1f0
> > [   15.353088]  ksys_read+0x74/0x100
> > [   15.356390]  __arm64_sys_read+0x28/0x34
> > ...
> >
> > This bug introduced by commit b261dba2fdb2 ("arm64: kdump: Remove custom
> > linux,usable-memory-range handling"), which moves
> > memblock_cap_memory_range() to fdt, but it breaches the rules that
> > memblock_cap_memory_range() should come after memblock_add() etc as said
> > in commit e888fa7bb882 ("memblock: Check memory add/cap ordering").
> >
> > As a consequence, the virtual address set up by copy_oldmem_page() does
> > not bail out from the test of virt_addr_valid() in check_heap_object(),
> > and finally hits the BUG_ON().
> >
> > Since memblock allocator has no idea about when the memblock is fully
> > populated, while efi_init() is aware, so tackling this issue by calling the
> > interface early_init_dt_check_for_usable_mem_range() exposed by of/fdt.
> >
> > Fixes: b261dba2fdb2 ("arm64: kdump: Remove custom linux,usable-memory-range handling")
> > Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: Zhen Lei <thunder.leizhen@huawei.com>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Will Deacon <will@kernel.org>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Mike Rapoport <rppt@kernel.org>
> > Cc: Geert Uytterhoeven <geert+renesas@glider.be>
> > Cc: Frank Rowand <frowand.list@gmail.com>
> > Cc: Ard Biesheuvel <ardb@kernel.org>
> > Cc: Nick Terrell <terrelln@fb.com>
> > Cc: linux-arm-kernel@lists.infradead.org
> > To: devicetree@vger.kernel.org
> > To: linux-efi@vger.kernel.org
> > ---
> >  drivers/firmware/efi/efi-init.c | 7 +++++++
> >  drivers/of/fdt.c                | 2 +-
> >  include/linux/of_fdt.h          | 1 +
> >  3 files changed, 9 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/firmware/efi/efi-init.c b/drivers/firmware/efi/efi-init.c
> > index b19ce1a83f91..82d986016fa9 100644
> > --- a/drivers/firmware/efi/efi-init.c
> > +++ b/drivers/firmware/efi/efi-init.c
> > @@ -235,6 +235,13 @@ void __init efi_init(void)
> >         }
> >
> >         reserve_regions();
> > +#ifdef CONFIG_OF_FLATTREE
> 
> Add a static inline stub to avoid this ifdef.
> 
Thanks for the suggestion.

I will follow up with V3 to this patch.

Regards,

	Pingfan

> > +       /*
> > +        * For memblock manipulation, the cap should come after the memblock_add().
> > +        * And now, memblock is fully populated, it is time to do capping.
> > +        */
> > +       early_init_dt_check_for_usable_mem_range();
> > +#endif
> >         efi_esrt_init();
> >         efi_mokvar_table_init();
> >
> > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > index 18a2df431bfd..aa07ef5cab5f 100644
> > --- a/drivers/of/fdt.c
> > +++ b/drivers/of/fdt.c
> > @@ -972,7 +972,7 @@ static unsigned long chosen_node_offset = -FDT_ERR_NOTFOUND;
> >   * location from flat tree
> >   * @node: reference to node containing usable memory range location ('chosen')
> >   */
> > -static void __init early_init_dt_check_for_usable_mem_range(void)
> > +void __init early_init_dt_check_for_usable_mem_range(void)
> >  {
> >         const __be32 *prop;
> >         int len;
> > diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
> > index cf48983d3c86..1d5ee19fadf7 100644
> > --- a/include/linux/of_fdt.h
> > +++ b/include/linux/of_fdt.h
> > @@ -62,6 +62,7 @@ extern int early_init_dt_scan_chosen(unsigned long node, const char *uname,
> >                                      int depth, void *data);
> >  extern int early_init_dt_scan_memory(unsigned long node, const char *uname,
> >                                      int depth, void *data);
> > +extern void early_init_dt_check_for_usable_mem_range(void);
> >  extern int early_init_dt_scan_chosen_stdout(void);
> >  extern void early_init_fdt_scan_reserved_mem(void);
> >  extern void early_init_fdt_reserve_self(void);
> > --
> > 2.31.1
> >
> 
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