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From: Hao Ge In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Stat-Signature: 3yj7ugerywcppoj4yxd9deqxkn4piwew X-Rspamd-Queue-Id: 76F8F4000B X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1733856391-327934 X-HE-Meta: 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 lOR5r8q4 3eUSDQrsGv25m4Xc+jmIggH9HxtU7SyZ8rAVK1ZjEiq6k075QmHPSz0BtZs7YblLB9ohfwnXfwNHSwCcGl9lHk+/+kuQWYl2AxNdMehVvrIU7ItG/QkjY9WmifGPoQSNgDHeiKFu3+7Uvhc2t+a0rEMaGy95ycv1f0CwUiQDTOsxkgpuBu2POtD8wYVfG41VrNtsQM12i/Qj4U1XP+8O1F0VVNY+R/BPrqU2wLBJKgo0C6+KzJY4Lq4uE6D19iyLYmw6w31jVU8p6VA0PF0D5G5N/WawUhlXWGpFposBN6yEkD/i3kUKP2afteREcJQaQlz1Ck7WcuKe6JFN6qWD2pvdcq1RzdAGLS9LRKwXMlntamiwchSQ9Dy+lFdjUxkDGRh8xiGjG0wyWFRX5rwCwFyt20C3VHNBGiMFF+zmOLSdz8Zw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Suren Thanks for your review. On 12/11/24 01:55, Suren Baghdasaryan wrote: > On Mon, Dec 9, 2024 at 10:53 PM Hao Ge wrote: >> From: Hao Ge >> >> 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_tags region, >> similar to how it is done for execmem_vmalloc. >> >> The difference is that our module_tags are allocated on demand, >> so similarly,we also need to allocate shadow memory regions on demand. >> However, we still need to adhere to the MODULE_ALIGN principle. >> >> 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] >> [ 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 >> Closes: https://lore.kernel.org/all/1ba0cc57-e2ed-caa2-1241-aa5615bee01f@candelatech.com/ >> Signed-off-by: Hao Ge >> --- >> 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 | 12 ++++++++++++ >> 1 file changed, 12 insertions(+) >> >> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c >> index f942408b53ef..bd3ee57ea13f 100644 >> --- a/lib/alloc_tag.c >> +++ b/lib/alloc_tag.c >> @@ -10,6 +10,7 @@ >> #include >> #include >> #include >> +#include >> >> #define ALLOCINFO_FILE_NAME "allocinfo" >> #define MODULE_ALLOC_TAG_VMAP_SIZE (100000UL * sizeof(struct alloc_tag)) >> @@ -422,6 +423,17 @@ static int vm_module_tags_populate(void) >> 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, >> + * it does so in units of pages. >> + * Therefore, here we need to align to MODULE_ALIGN. >> + */ >> + if ((phys_end & (MODULE_ALIGN - 1)) == 0) > phys_end is calculated as: > > unsigned long phys_end = ALIGN_DOWN(module_tags.start_addr, PAGE_SIZE) + > (vm_module_tags->nr_pages > << PAGE_SHIFT); > > and therefore is always PAGE_SIZE-aligned. PAGE_SIZE is always a > multiple of MODULE_ALIGN, therefore phys_end is always When CONFIG_KASAN_VMALLOC is not enabled #define MODULE_ALIGN (PAGE_SIZE << KASAN_SHADOW_SCALE_SHIFT) https://elixir.bootlin.com/linux/v6.13-rc2/source/include/linux/execmem.h#L11 and On x86, KASAN_SHADOW_SCALE_SHIFT is set to 3 https://elixir.bootlin.com/linux/v6.13-rc2/source/arch/x86/include/asm/kasan.h#L7 As mentioned in my comment, Kasan allocates 1 byte of shadow for every 8 bytes of data So, when you allocate a shadow page through kasan_alloc_module_shadow, it corresponds to eight physical pages in our system. So, we need MODULE_ALIGN to ensure proper alignment when allocating shadow memory for modules using KASAN. Let's take a look at the kasan_alloc_module_shadow function again As I mentioned earlier,Kasan allocates 1 byte of shadow for every 8 bytes of data. Assuming phys_end is set to 0 for the sake of this example, if you allocate a single shadow page, the corresponding address range it can represent would be [0, 0x7FFFF]. So, it is incorrect to call kasan_alloc_module_shadow every time a page is allocated, as it can trigger warnings in the system. https://elixir.bootlin.com/linux/v6.13-rc2/source/mm/kasan/shadow.c#L599 Thanks Best Regards Hao > MODULE_ALIGN-aligned and the above condition is not needed. > >> + kasan_alloc_module_shadow((void *)phys_end, >> + round_up(nr << PAGE_SHIFT, MODULE_ALIGN), > Here again, (nr << PAGE_SHIFT) is PAGE_SIZE-aligned and PAGE_SIZE is a > multiple of MODULE_ALIGN, therefore (nr << PAGE_SHIFT) is always > multiple of MODULE_ALIGN and there is no need for round_up(). > > IOW, I think this patch should simply add one line: > > vm_module_tags->nr_pages += nr; > + kasan_alloc_module_shadow((void *)phys_end, nr << > PAGE_SHIFT, GFP_KERNEL); > > Am I missing something? > >> + GFP_KERNEL); >> } >> >> /* >> -- >> 2.25.1 >>