linux-kernel - [PATCH] resource,kexec: walk_system_ram_res

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Message-ID: <20241017190347.5578-1-gourry@gourry.net>
Date: Thu, 17 Oct 2024 15:03:47 -0400
From: Gregory Price <gourry@...rry.net>
To: kexec@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	bhelgaas@...gle.com,
	andriy.shevchenko@...ux.intel.com,
	ilpo.jarvinen@...ux.intel.com,
	mika.westerberg@...ux.intel.com,
	ying.huang@...el.com,
	bhe@...hat.com,
	gourry@...rry.net,
	tglx@...utronix.de,
	takahiro.akashi@...aro.org,
	stable@...r.kernel.org
Subject: [PATCH] resource,kexec: walk_system_ram_res_rev must retain resource flags

walk_system_ram_res_rev() erroneously discards resource flags when
passing the information to the callback.

This causes systems with IORESOURCE_SYSRAM_DRIVER_MANAGED memory to
have these resources selected during kexec to store kexec buffers
if that memory happens to be at placed above normal system ram.

This leads to undefined behavior after reboot. If the kexec buffer
is never touched, nothing happens. If the kexec buffer is touched,
it could lead to a crash (like below) or undefined behavior.

Tested on a system with CXL memory expanders with driver managed
memory, TPM enabled, and CONFIG_IMA_KEXEC=y. Adding printk's
showed the flags were being discarded and as a result the check
for IORESOURCE_SYSRAM_DRIVER_MANAGED passes.

find_next_iomem_res: name(System RAM (kmem))
		     start(10000000000)
		     end(1034fffffff)
		     flags(83000200)

locate_mem_hole_top_down: start(10000000000) end(1034fffffff) flags(0)

[.] BUG: unable to handle page fault for address: ffff89834ffff000
[.] #PF: supervisor read access in kernel mode
[.] #PF: error_code(0x0000) - not-present page
[.] PGD c04c8bf067 P4D c04c8bf067 PUD c04c8be067 PMD 0
[.] Oops: 0000 [#1] SMP
[.] RIP: 0010:ima_restore_measurement_list+0x95/0x4b0
[.] RSP: 0018:ffffc900000d3a80 EFLAGS: 00010286
[.] RAX: 0000000000001000 RBX: 0000000000000000 RCX: ffff89834ffff000
[.] RDX: 0000000000000018 RSI: ffff89834ffff000 RDI: ffff89834ffff018
[.] RBP: ffffc900000d3ba0 R08: 0000000000000020 R09: ffff888132b8a900
[.] R10: 4000000000000000 R11: 000000003a616d69 R12: 0000000000000000
[.] R13: ffffffff8404ac28 R14: 0000000000000000 R15: ffff89834ffff000
[.] FS:  0000000000000000(0000) GS:ffff893d44640000(0000) knlGS:0000000000000000
[.] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[.] ata5: SATA link down (SStatus 0 SControl 300)
[.] CR2: ffff89834ffff000 CR3: 000001034d00f001 CR4: 0000000000770ef0
[.] PKRU: 55555554
[.] Call Trace:
[.]  <TASK>
[.]  ? __die+0x78/0xc0
[.]  ? page_fault_oops+0x2a8/0x3a0
[.]  ? exc_page_fault+0x84/0x130
[.]  ? asm_exc_page_fault+0x22/0x30
[.]  ? ima_restore_measurement_list+0x95/0x4b0
[.]  ? template_desc_init_fields+0x317/0x410
[.]  ? crypto_alloc_tfm_node+0x9c/0xc0
[.]  ? init_ima_lsm+0x30/0x30
[.]  ima_load_kexec_buffer+0x72/0xa0
[.]  ima_init+0x44/0xa0
[.]  __initstub__kmod_ima__373_1201_init_ima7+0x1e/0xb0
[.]  ? init_ima_lsm+0x30/0x30
[.]  do_one_initcall+0xad/0x200
[.]  ? idr_alloc_cyclic+0xaa/0x110
[.]  ? new_slab+0x12c/0x420
[.]  ? new_slab+0x12c/0x420
[.]  ? number+0x12a/0x430
[.]  ? sysvec_apic_timer_interrupt+0xa/0x80
[.]  ? asm_sysvec_apic_timer_interrupt+0x16/0x20
[.]  ? parse_args+0xd4/0x380
[.]  ? parse_args+0x14b/0x380
[.]  kernel_init_freeable+0x1c1/0x2b0
[.]  ? rest_init+0xb0/0xb0
[.]  kernel_init+0x16/0x1a0
[.]  ret_from_fork+0x2f/0x40
[.]  ? rest_init+0xb0/0xb0
[.]  ret_from_fork_asm+0x11/0x20
[.]  </TASK>

Link: https://lore.kernel.org/all/20231114091658.228030-1-bhe@redhat.com/
Fixes: 7acf164b259d ("resource: add walk_system_ram_res_rev()")
Cc: stable@...r.kernel.org
Signed-off-by: Gregory Price <gourry@...rry.net>
---
 kernel/resource.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index b730bd28b422..4101016e8b20 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -459,9 +459,7 @@ int walk_system_ram_res_rev(u64 start, u64 end, void *arg,
 			rams_size += 16;
 		}
 
-		rams[i].start = res.start;
-		rams[i++].end = res.end;
-
+		rams[i++] = res;
 		start = res.end + 1;
 	}
 
-- 
2.43.0