CVE-2023-52506: NULL Pointer Dereference

In the Linux kernel, the following vulnerability has been resolved:

LoongArch: Set all reserved memblocks on Node#0 at initialization

After commit 61167ad5fecdea ("mm: pass nid to reserve_bootmem_region()") we get a panic if DEFERRED_STRUCT_PAGE_INIT is enabled:

[ 0.000000] CPU 0 Unable to handle kernel paging request at virtual address 0000000000002b82, era == 90000000040e3f28, ra == 90000000040e3f18 [ 0.000000] Oops[#1]: [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 6.5.0+ #733 [ 0.000000] pc 90000000040e3f28 ra 90000000040e3f18 tp 90000000046f4000 sp 90000000046f7c90 [ 0.000000] a0 0000000000000001 a1 0000000000200000 a2 0000000000000040 a3 90000000046f7ca0 [ 0.000000] a4 90000000046f7ca4 a5 0000000000000000 a6 90000000046f7c38 a7 0000000000000000 [ 0.000000] t0 0000000000000002 t1 9000000004b00ac8 t2 90000000040e3f18 t3 90000000040f0800 [ 0.000000] t4 00000000000f0000 t5 80000000ffffe07e t6 0000000000000003 t7 900000047fff5e20 [ 0.000000] t8 aaaaaaaaaaaaaaab u0 0000000000000018 s9 0000000000000000 s0 fffffefffe000000 [ 0.000000] s1 0000000000000000 s2 0000000000000080 s3 0000000000000040 s4 0000000000000000 [ 0.000000] s5 0000000000000000 s6 fffffefffe000000 s7 900000000470b740 s8 9000000004ad4000 [ 0.000000] ra: 90000000040e3f18 reserve_bootmem_region+0xec/0x21c [ 0.000000] ERA: 90000000040e3f28 reserve_bootmem_region+0xfc/0x21c [ 0.000000] CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) [ 0.000000] PRMD: 00000000 (PPLV0 -PIE -PWE) [ 0.000000] EUEN: 00000000 (-FPE -SXE -ASXE -BTE) [ 0.000000] ECFG: 00070800 (LIE=11 VS=7) [ 0.000000] ESTAT: 00010800 [PIL] (IS=11 ECode=1 EsubCode=0) [ 0.000000] BADV: 0000000000002b82 [ 0.000000] PRID: 0014d000 (Loongson-64bit, Loongson-3A6000) [ 0.000000] Modules linked in: [ 0.000000] Process swapper (pid: 0, threadinfo=(____ptrval____), task=(____ptrval____)) [ 0.000000] Stack : 0000000000000000 9000000002eb5430 0000003a00000020 90000000045ccd00 [ 0.000000] 900000000470e000 90000000002c1918 0000000000000000 9000000004110780 [ 0.000000] 00000000fe6c0000 0000000480000000 9000000004b4e368 9000000004110748 [ 0.000000] 0000000000000000 900000000421ca84 9000000004620000 9000000004564970 [ 0.000000] 90000000046f7d78 9000000002cc9f70 90000000002c1918 900000000470e000 [ 0.000000] 9000000004564970 90000000040bc0e0 90000000046f7d78 0000000000000000 [ 0.000000] 0000000000004000 90000000045ccd00 0000000000000000 90000000002c1918 [ 0.000000] 90000000002c1900 900000000470b700 9000000004b4df78 9000000004620000 [ 0.000000] 90000000046200a8 90000000046200a8 0000000000000000 9000000004218b2c [ 0.000000] 9000000004270008 0000000000000001 0000000000000000 90000000045ccd00 [ 0.000000] ... [ 0.000000] Call Trace: [ 0.000000] [<90000000040e3f28>] reserve_bootmem_region+0xfc/0x21c [ 0.000000] [<900000000421ca84>] memblock_free_all+0x114/0x350 [ 0.000000] [<9000000004218b2c>] mm_core_init+0x138/0x3cc [ 0.000000] [<9000000004200e38>] start_kernel+0x488/0x7a4 [ 0.000000] [<90000000040df0d8>] kernel_entry+0xd8/0xdc [ 0.000000] [ 0.000000] Code: 02eb21ad 00410f4c 380c31ac <262b818d> 6800b70d 02c1c196 0015001c 57fe4bb1 260002cd

The reason is early memblock_reserve() in memblock_init() set node id to MAX_NUMNODES, making NODE_DATA(nid) a NULL dereference in the call chain reserve_bootmem_region() -> init_reserved_page(). After memblock_init(), those late calls of memblock_reserve() operate on subregions of memblock .memory regions. As a result, these reserved regions will be set to the correct node at the first iteration of memmap_init_reserved_pages().

So set all reserved memblocks on Node#0 at initialization can avoid this panic.