[PATCH v6] mm/alloc_tag: Fix panic when CONFIG_KASAN enabled and CONFIG_KASAN_VMALLOC not enabled
From: Hao Ge
Date: Thu Dec 12 2024 - 02:22:40 EST
From: Hao Ge <gehao@xxxxxxxxxx>
When CONFIG_KASAN is enabled but CONFIG_KASAN_VMALLOC
is not enabled, we may encounter a panic during system boot.
Because we haven't allocated pages and created mappings
for the shadow memory corresponding to module allocation tags
region,similar to how it is done for execmem_vmalloc.
The memory for module allocation tags is allocated on demand,
therefore we need to allocate shadow memory on demand as well in
MODULE_ALIGN blocks.
Here is the log for panic:
[ 18.349421] BUG: unable to handle page fault for address: fffffbfff8092000
[ 18.350016] #PF: supervisor read access in kernel mode
[ 18.350459] #PF: error_code(0x0000) - not-present page
[ 18.350904] PGD 20fe52067 P4D 219dc8067 PUD 219dc4067 PMD 102495067 PTE 0
[ 18.351484] Oops: Oops: 0000 [#1] PREEMPT SMP KASAN NOPTI
[ 18.351961] CPU: 5 UID: 0 PID: 1 Comm: systemd Not tainted 6.13.0-rc1+ #3
[ 18.352533] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 18.353494] RIP: 0010:kasan_check_range+0xba/0x1b0
[ 18.353931] Code: 8d 5a 07 4c 0f 49 da 49 c1 fb 03 45 85 db 0f 84 dd 00 00 00 45 89 db 4a 8d 14 d8 eb 0d 48 83 c0 08 48 39 c2 0f 84 c1 00 00 00 <48> 83 38 00 74 ed 48 8d 50 08 eb 0d 48 83 c0 01 48 39 d0 0f 84 90
[ 18.355484] RSP: 0018:ff11000101877958 EFLAGS: 00010206
[ 18.355937] RAX: fffffbfff8092000 RBX: fffffbfff809201e RCX: ffffffff82a7ceac
[ 18.356542] RDX: fffffbfff8092018 RSI: 00000000000000f0 RDI: ffffffffc0490000
[ 18.357153] RBP: fffffbfff8092000 R08: 0000000000000001 R09: fffffbfff809201d
[ 18.357756] R10: ffffffffc04900ef R11: 0000000000000003 R12: ffffffffc0490000
[ 18.358365] R13: ff11000101877b48 R14: ffffffffc0490000 R15: 000000000000002c
[ 18.358968] FS: 00007f9bd13c5940(0000) GS:ff110001eb480000(0000) knlGS:0000000000000000
[ 18.359648] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 18.360178] CR2: fffffbfff8092000 CR3: 0000000109214004 CR4: 0000000000771ef0
[ 18.360790] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 18.361404] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 18.362020] PKRU: 55555554
[ 18.362261] Call Trace:
[ 18.362481] <TASK>
[ 18.362671] ? __die+0x23/0x70
[ 18.362964] ? page_fault_oops+0xc2/0x160
[ 18.363318] ? exc_page_fault+0xad/0xc0
[ 18.363680] ? asm_exc_page_fault+0x26/0x30
[ 18.364056] ? move_module+0x3cc/0x8a0
[ 18.364398] ? kasan_check_range+0xba/0x1b0
[ 18.364755] __asan_memcpy+0x3c/0x60
[ 18.365074] move_module+0x3cc/0x8a0
[ 18.365386] layout_and_allocate.constprop.0+0x3d5/0x720
[ 18.365841] ? early_mod_check+0x3dc/0x510
[ 18.366195] load_module+0x72/0x1850
[ 18.366509] ? __pfx_kernel_read_file+0x10/0x10
[ 18.366918] ? vm_mmap_pgoff+0x21c/0x2d0
[ 18.367262] init_module_from_file+0xd1/0x130
[ 18.367638] ? __pfx_init_module_from_file+0x10/0x10
[ 18.368073] ? __pfx__raw_spin_lock+0x10/0x10
[ 18.368456] ? __pfx_cred_has_capability.isra.0+0x10/0x10
[ 18.368938] idempotent_init_module+0x22c/0x790
[ 18.369332] ? simple_getattr+0x6f/0x120
[ 18.369676] ? __pfx_idempotent_init_module+0x10/0x10
[ 18.370110] ? fdget+0x58/0x3a0
[ 18.370393] ? security_capable+0x64/0xf0
[ 18.370745] __x64_sys_finit_module+0xc2/0x140
[ 18.371136] do_syscall_64+0x7d/0x160
[ 18.371459] ? fdget_pos+0x1c8/0x4c0
[ 18.371784] ? ksys_read+0xfd/0x1d0
[ 18.372106] ? syscall_exit_to_user_mode+0x10/0x1f0
[ 18.372525] ? do_syscall_64+0x89/0x160
[ 18.372860] ? do_syscall_64+0x89/0x160
[ 18.373194] ? do_syscall_64+0x89/0x160
[ 18.373527] ? syscall_exit_to_user_mode+0x10/0x1f0
[ 18.373952] ? do_syscall_64+0x89/0x160
[ 18.374283] ? syscall_exit_to_user_mode+0x10/0x1f0
[ 18.374701] ? do_syscall_64+0x89/0x160
[ 18.375037] ? do_user_addr_fault+0x4a8/0xa40
[ 18.375416] ? clear_bhb_loop+0x25/0x80
[ 18.375748] ? clear_bhb_loop+0x25/0x80
[ 18.376119] ? clear_bhb_loop+0x25/0x80
[ 18.376450] entry_SYSCALL_64_after_hwframe+0x76/0x7e
Fixes: 233e89322cbe ("alloc_tag: fix module allocation tags populated area calculation")
Reported-by: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/1ba0cc57-e2ed-caa2-1241-aa5615bee01f@xxxxxxxxxxxxxxx/
Suggested-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Acked-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Signed-off-by: Hao Ge <gehao@xxxxxxxxxx>
---
v6: In the previous version, there was an omission
in the commit message where "module_tags"
should have been replaced with "module allocation tags".
v5: Modify the commit message based on Suren's suggestions
Add Acked-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
v4: Based on Suren's suggestion for modification (to make the code simpler),
modify the code.
Update the comments in the code due to the modifications made to the code.
Add Suggested-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
v3: Adjusting the title because the previous one was a bit unclear.
Suren has pointed out that our condition for determining whether
to allocate shadow memory is unreasonable.We have adjusted our method
to use every 8 pages as an index (idx), and we will make decisions based
on this idx when determining whether to allocate shadow memory.
v2: Add comments to facilitate understanding of the code.
Add align nr << PAGE_SHIFT to MODULE_ALIGN,even though kasan_alloc_module_shadow
already handles this internally,but to make the code more readable and user-friendly
commit 233e89322cbe ("alloc_tag: fix module allocation
tags populated area calculation") is currently in the
mm-hotfixes-unstable branch, so this patch is
developed based on the mm-hotfixes-unstable branch.
---
lib/alloc_tag.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index f942408b53ef..c5bdfa297a35 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -407,6 +407,8 @@ static int vm_module_tags_populate(void)
if (phys_end < new_end) {
struct page **next_page = vm_module_tags->pages + vm_module_tags->nr_pages;
+ unsigned long old_shadow_end = ALIGN(phys_end, MODULE_ALIGN);
+ unsigned long new_shadow_end = ALIGN(new_end, MODULE_ALIGN);
unsigned long more_pages;
unsigned long nr;
@@ -421,7 +423,19 @@ static int vm_module_tags_populate(void)
__free_page(next_page[i]);
return -ENOMEM;
}
+
vm_module_tags->nr_pages += nr;
+
+ /*
+ * Kasan allocates 1 byte of shadow for every 8 bytes of data.
+ * When kasan_alloc_module_shadow allocates shadow memory,
+ * its unit of allocation is a page.
+ * Therefore, here we need to align to MODULE_ALIGN.
+ */
+ if (old_shadow_end < new_shadow_end)
+ kasan_alloc_module_shadow((void *)old_shadow_end,
+ new_shadow_end - old_shadow_end,
+ GFP_KERNEL);
}
/*
--
2.25.1