+Zhen Lei
On Mon, Dec 13, 2021 at 7:48 AM Pingfan Liu <kernelfans@xxxxxxxxx> wrote:
>
> 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").
Presumably only when using EFI boot which throws out any DT memblock setup.
>
> 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 the time point of the full
> memblock's population, resolving this issue at arch level code by
> calling a new interface early_init_dt_cap_memory_range() exposed by fdt.
>
> Fixes: b261dba2fdb2 ("arm64: kdump: Remove custom linux,usable-memory-range handling")
> Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Mike Rapoport <rppt@xxxxxxxxxx>
> Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> Cc: Frank Rowand <frowand.list@xxxxxxxxx>
> Cc: Nick Terrell <terrelln@xxxxxx>
> To: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> To: devicetree@xxxxxxxxxxxxxxx
> ---
> arch/arm64/kernel/setup.c | 1 +
> drivers/of/fdt.c | 5 +++++
> include/linux/of_fdt.h | 1 +
> 3 files changed, 7 insertions(+)
>
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index be5f85b0a24d..353e5171a66c 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -331,6 +331,7 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
>
> xen_early_init();
> efi_init();
> + early_init_dt_cap_memory_range();
As it is efi_init() that does all the memblock setup, I think this
belongs in efi_init() because it would be needed for any arch that
uses EFI for memory setup.
>
> if (!efi_enabled(EFI_BOOT) && ((u64)_text % MIN_KIMG_ALIGN) != 0)
> pr_warn(FW_BUG "Kernel image misaligned at boot, please fix your bootloader!");
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index bdca35284ceb..bb7e8fc3a334 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -1278,6 +1278,11 @@ void __init early_init_dt_scan_nodes(void)
> memblock_cap_memory_range(cap_mem_addr, cap_mem_size);
> }
>
> +void __init early_init_dt_cap_memory_range(void)
> +{
> + memblock_cap_memory_range(cap_mem_addr, cap_mem_size);
This code is changing in [1] which I think should make fixing this
issue easier. I'd suggest making
early_init_dt_check_for_usable_mem_range() non-static and the EFI code
can call it.
I'm also curious how folks testing that series don't hit this issue.
Rob
[1] https://lore.kernel.org/all/20211210065533.2023-9-thunder.leizhen@xxxxxxxxxx/
