6.6-stable review patch. If anyone has any objections, please let me know.
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From: Christophe Leroy christophe.leroy@csgroup.eu
[ Upstream commit d262a192d38e527faa5984629aabda2e0d1c4f54 ]
Erhard reported the following KASAN hit while booting his PowerMac G4 with a KASAN-enabled kernel 6.13-rc6:
BUG: KASAN: vmalloc-out-of-bounds in copy_to_kernel_nofault+0xd8/0x1c8 Write of size 8 at addr f1000000 by task chronyd/1293
CPU: 0 UID: 123 PID: 1293 Comm: chronyd Tainted: G W 6.13.0-rc6-PMacG4 #2 Tainted: [W]=WARN Hardware name: PowerMac3,6 7455 0x80010303 PowerMac Call Trace: [c2437590] [c1631a84] dump_stack_lvl+0x70/0x8c (unreliable) [c24375b0] [c0504998] print_report+0xdc/0x504 [c2437610] [c050475c] kasan_report+0xf8/0x108 [c2437690] [c0505a3c] kasan_check_range+0x24/0x18c [c24376a0] [c03fb5e4] copy_to_kernel_nofault+0xd8/0x1c8 [c24376c0] [c004c014] patch_instructions+0x15c/0x16c [c2437710] [c00731a8] bpf_arch_text_copy+0x60/0x7c [c2437730] [c0281168] bpf_jit_binary_pack_finalize+0x50/0xac [c2437750] [c0073cf4] bpf_int_jit_compile+0xb30/0xdec [c2437880] [c0280394] bpf_prog_select_runtime+0x15c/0x478 [c24378d0] [c1263428] bpf_prepare_filter+0xbf8/0xc14 [c2437990] [c12677ec] bpf_prog_create_from_user+0x258/0x2b4 [c24379d0] [c027111c] do_seccomp+0x3dc/0x1890 [c2437ac0] [c001d8e0] system_call_exception+0x2dc/0x420 [c2437f30] [c00281ac] ret_from_syscall+0x0/0x2c --- interrupt: c00 at 0x5a1274 NIP: 005a1274 LR: 006a3b3c CTR: 005296c8 REGS: c2437f40 TRAP: 0c00 Tainted: G W (6.13.0-rc6-PMacG4) MSR: 0200f932 <VEC,EE,PR,FP,ME,IR,DR,RI> CR: 24004422 XER: 00000000
GPR00: 00000166 af8f3fa0 a7ee3540 00000001 00000000 013b6500 005a5858 0200f932 GPR08: 00000000 00001fe9 013d5fc8 005296c8 2822244c 00b2fcd8 00000000 af8f4b57 GPR16: 00000000 00000001 00000000 00000000 00000000 00000001 00000000 00000002 GPR24: 00afdbb0 00000000 00000000 00000000 006e0004 013ce060 006e7c1c 00000001 NIP [005a1274] 0x5a1274 LR [006a3b3c] 0x6a3b3c --- interrupt: c00
The buggy address belongs to the virtual mapping at [f1000000, f1002000) created by: text_area_cpu_up+0x20/0x190
The buggy address belongs to the physical page: page: refcount:1 mapcount:0 mapping:00000000 index:0x0 pfn:0x76e30 flags: 0x80000000(zone=2) raw: 80000000 00000000 00000122 00000000 00000000 00000000 ffffffff 00000001 raw: 00000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: f0ffff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f0ffff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
f1000000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
^ f1000080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f1000100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ==================================================================
f8 corresponds to KASAN_VMALLOC_INVALID which means the area is not initialised hence not supposed to be used yet.
Powerpc text patching infrastructure allocates a virtual memory area using get_vm_area() and flags it as VM_ALLOC. But that flag is meant to be used for vmalloc() and vmalloc() allocated memory is not supposed to be used before a call to __vmalloc_node_range() which is never called for that area.
That went undetected until commit e4137f08816b ("mm, kasan, kmsan: instrument copy_from/to_kernel_nofault")
The area allocated by text_area_cpu_up() is not vmalloc memory, it is mapped directly on demand when needed by map_kernel_page(). There is no VM flag corresponding to such usage, so just pass no flag. That way the area will be unpoisonned and usable immediately.
Reported-by: Erhard Furtner erhard_f@mailbox.org Closes: https://lore.kernel.org/all/20250112135832.57c92322@yea/ Fixes: 37bc3e5fd764 ("powerpc/lib/code-patching: Use alternate map for patch_instruction()") Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu Signed-off-by: Madhavan Srinivasan maddy@linux.ibm.com Link: https://patch.msgid.link/06621423da339b374f48c0886e3a5db18e896be8.1739342693... Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/lib/code-patching.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c index b00112d7ad467..4426a77c8f063 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -105,7 +105,7 @@ static int text_area_cpu_up(unsigned int cpu) unsigned long addr; int err;
- area = get_vm_area(PAGE_SIZE, VM_ALLOC); + area = get_vm_area(PAGE_SIZE, 0); if (!area) { WARN_ONCE(1, "Failed to create text area for cpu %d\n", cpu);