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
31854f3ecfd6 ("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
4ab44472e089 ("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: 31854f3ecfd6 ("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
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211215021348.8766-1-kernelfans@gmail.com
}
reserve_regions();
+ /*
+ * 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();
efi_esrt_init();
efi_mokvar_table_init();
* early_init_dt_check_for_usable_mem_range - Decode usable memory range
* location from flat tree
*/
-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;
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);
extern void early_init_devtree(void *);
extern void early_get_first_memblock_info(void *, phys_addr_t *);
#else /* CONFIG_OF_EARLY_FLATTREE */
+static inline void early_init_dt_check_for_usable_mem_range(void) {}
static inline int early_init_dt_scan_chosen_stdout(void) { return -ENODEV; }
static inline void early_init_fdt_scan_reserved_mem(void) {}
static inline void early_init_fdt_reserve_self(void) {}
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