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2025 18:06:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 952E3C4CEF7; Sat, 29 Nov 2025 18:06:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1764439619; bh=nHDT+vnVr9ZxoQNQJxT+ttjh4quzdU+UxPDtwJWJq9Y=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=imequqQ+pT6INKeFynsxEJTEi5ZQUOItUSepXeIIj0XlNMIRMi2GdRFp1LsQlnirL Ibr6hf35eNoBXFqol2lu4UpPb4GkIS3TOn2Y5YI+pLWuYA6hDM5l36aflaAbALkxVc FLdxZYEfksXfgRkwCy+oGFJKtKjO/B2SCEXq39VA= Date: Sat, 29 Nov 2025 10:06:58 -0800 From: Andrew Morton To: Yeoreum Yun Cc: catalin.marinas@arm.com, kevin.brodsky@arm.com, ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, vincenzo.frascino@arm.com, urezki@gmail.com, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, stable@vger.kernel.org, Jiayuan Chen Subject: Re: [PATCH] kasan: hw_tags: fix a false positive case of vrealloc in alloced size Message-Id: <20251129100658.6b25799da5ace00c3a6d0f42@linux-foundation.org> In-Reply-To: <20251129123648.1785982-1-yeoreum.yun@arm.com> References: <20251129123648.1785982-1-yeoreum.yun@arm.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 12FEE40011 X-Rspamd-Server: rspam02 X-Stat-Signature: febexsp69nu5xjf9ys6uceckj3apegz8 X-Rspam-User: X-HE-Tag: 1764439619-192504 X-HE-Meta: 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 IPfr9vuW CTdTjUPtaRk2QlW0Ns9l+Hq/owFmso6Moj1pod4FMn+ViKgHiheNQOSyjfUcr8yJ1IcmWw7G/PWuHKQ7+/LvMQd+vlYTR/k8mWycbCVt+hUiSN89Ao2AIIhAp0Ar4wiknsD82LfGTKc2TgTFDHVAMSavy5+VJ2rToP6MM9C8mv3fAzDJtHMzCFJSDa/jz+EIWHUhRk1foRnMksW82rxEqPhrTXwemqD+FknxEe16UBu0Xqg2JaP7jwo3u2FhFqLhn0+Ljsi/X0A+eYXIaJoQGWmJNh7VjJEJfV+6NtMbwO5cDonIUpx1h1GN7AMqDjJSaRtIymZ3fFZoIqzAMOuOdB2zK8tJf/EdVKupNRUDIzO/MnkDhqFxCS8Xe7ePnZT+XcAMo7HuiPC7E0aa/x9fjsV1uZP1KQpJJiP2JiIAl+iwJJLz/5HDvc+QGoDEQjPhTo8dJKVdL15dSjxUM/QSKV7tx+0elz29dPf7v 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: On Sat, 29 Nov 2025 12:36:47 +0000 Yeoreum Yun wrote: > When a memory region is allocated with vmalloc() and later expanded with > vrealloc() — while still within the originally allocated size — > KASAN may report a false positive because > it does not update the tags for the newly expanded portion of the memory. > > A typical example of this pattern occurs in the BPF verifier, > and the following is a related false positive report: > > [ 2206.486476] ================================================================== > [ 2206.486509] BUG: KASAN: invalid-access in __memcpy+0xc/0x30 > [ 2206.486607] Write at addr f5ff800083765270 by task test_progs/205 > [ 2206.486664] Pointer tag: [f5], memory tag: [fe] > [ 2206.486703] > [ 2206.486745] CPU: 4 UID: 0 PID: 205 Comm: test_progs Tainted: G OE 6.18.0-rc7+ #145 PREEMPT(full) > [ 2206.486861] Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE > [ 2206.486897] Hardware name: , BIOS > [ 2206.486932] Call trace: > [ 2206.486961] show_stack+0x24/0x40 (C) > [ 2206.487071] __dump_stack+0x28/0x48 > [ 2206.487182] dump_stack_lvl+0x7c/0xb0 > [ 2206.487293] print_address_description+0x80/0x270 > [ 2206.487403] print_report+0x94/0x100 > [ 2206.487505] kasan_report+0xd8/0x150 > [ 2206.487606] __do_kernel_fault+0x64/0x268 > [ 2206.487717] do_bad_area+0x38/0x110 > [ 2206.487820] do_tag_check_fault+0x38/0x60 > [ 2206.487936] do_mem_abort+0x48/0xc8 > [ 2206.488042] el1_abort+0x40/0x70 > [ 2206.488127] el1h_64_sync_handler+0x50/0x118 > [ 2206.488217] el1h_64_sync+0xa4/0xa8 > [ 2206.488303] __memcpy+0xc/0x30 (P) > [ 2206.488412] do_misc_fixups+0x4f8/0x1950 > [ 2206.488528] bpf_check+0x31c/0x840 > [ 2206.488638] bpf_prog_load+0x58c/0x658 > [ 2206.488737] __sys_bpf+0x364/0x488 > [ 2206.488833] __arm64_sys_bpf+0x30/0x58 > [ 2206.488920] invoke_syscall+0x68/0xe8 > [ 2206.489033] el0_svc_common+0xb0/0xf8 > [ 2206.489143] do_el0_svc+0x28/0x48 > [ 2206.489249] el0_svc+0x40/0xe8 > [ 2206.489337] el0t_64_sync_handler+0x84/0x140 > [ 2206.489427] el0t_64_sync+0x1bc/0x1c0 > > Here, 0xf5ff800083765000 is vmalloc()ed address for > env->insn_aux_data with the size of 0x268. > While this region is expanded size by 0x478 and initialise > increased region to apply patched instructions, > a false positive is triggered at the address 0xf5ff800083765270 > because __kasan_unpoison_vmalloc() with KASAN_VMALLOC_PROT_NORMAL flag only > doesn't update the tag on increaed region. > > To address this, introduces KASAN_VMALLOC_EXPAND flag which > is used to expand vmalloc()ed memory in range of real allocated size > to update tag for increased region. Thanks. > Fixes: 23689e91fb22 ("kasan, vmalloc: add vmalloc tagging for HW_TAGS”) > Cc: Unfortunately this is changing the same code as "mm/kasan: fix incorrect unpoisoning in vrealloc for KASAN", (https://lkml.kernel.org/r/20251128111516.244497-1-jiayuan.chen@linux.dev) which is also cc:stable. So could you please take a look at the code in mm.git's mm-hotfixes-unstable branch (git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm) and base the fix upon that? This way everything should merge and backport nicely.