From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EBD38349CF2; Thu, 2 Jul 2026 16:52:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783011135; cv=none; b=tg+QtJUn72BxeYGxKGtGZFj0YFkDiZx/o4Gb4/0UsbQmM3SqI1m7BS/lO5Se0QNgAgZaD+nqFuvmONY2I535oTeI/GL351Lvw2xQkwBgh2eGfTLtaatcZBQjTBRZFyoa1je4ZaZr9v9nGpippxjvxP1mVF6VU89zLwK4fAcKnKI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783011135; c=relaxed/simple; bh=9Xi0oRiJIITV7WkUMgcy9zhzWSFpqtN487pg8XsoN9M=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=g0OylnEezrMvixCzZoKvi6ShksxVbgnIB/c0wzOToT4O+GDy2e7P2j+3lcVVYMYfkrvsi4xWD/Rxc6j2o04ll5la3Wv8yQUzP8kn+c15aTwKsNfFRM2a0GP9i9vTlo9JaBx+sLIVNcDedCURXRy9X0LL5wY/hvdr36TPJQmV2cs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=ymx9lpt5; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ymx9lpt5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 637D81F000E9; Thu, 2 Jul 2026 16:52:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783011133; bh=0qF5dXZwkNBQzJvEvhU1vsmZXoRqf522ZFocOEeZQ5E=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=ymx9lpt5vVxjtMGz1qtL5+u3rhcezyts6FH5pw6E5Y/UrlBk6Qi0gwOza16GDyTuF hv0ElG+tYjX6e2PksC6JK7XOFTCLuyqilZPx6vDUZB5ZT4iDuEkiHVvcR0EjfvkWae iSIh7qOGIZXijbl6GiRN6tjLtLImCw5Hnq5jod/k= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Emil Tsalapatis , Jiayuan Chen , Yonghong Song , Zilin Guan , Dawei Feng , Alexei Starovoitov Subject: [PATCH 6.6 142/175] bpf: use kvfree() for replaced sysctl write buffer Date: Thu, 2 Jul 2026 18:20:43 +0200 Message-ID: <20260702155118.797232287@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260702155115.766838875@linuxfoundation.org> References: <20260702155115.766838875@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dawei Feng commit 4c21b5927d4364bfe7365f2700da5fea0ed0d004 upstream. proc_sys_call_handler() allocates its temporary sysctl buffer with kvzalloc() and passes it to __cgroup_bpf_run_filter_sysctl(). Since kvzalloc() may fall back to vmalloc() for large allocations, freeing that buffer with kfree() is wrong and can corrupt memory. Use kvfree() to safely handle both kmalloc and kvzalloc()/vmalloc allocations. The bug was first flagged by an experimental analysis tool we are developing for kernel memory-management bugs while analyzing v6.13-rc1. The tool is still under development and is not yet publicly available. Manual inspection confirms that the bug is still present in v7.1-rc5. Reproduced the bug based on v7.1-rc4 in a QEMU x86_64 guest booted with KASAN and CONFIG_FAILSLAB enabled. To exercise the replacement path, the test tree also included the accompanying fix for the stale ret == 1 check in __cgroup_bpf_run_filter_sysctl(). The reproducer confines failslab injections to the proc_sys_call_handler() range, uses stacktrace-depth=32, and injects fail-nth=1 while writing 8191 bytes to /proc/sys/kernel/domainname from a task in the target cgroup. Under that setup, fail-nth=1 triggered the fault: BUG: unable to handle page fault for address: ffffeb0200024d48 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 SMP KASAN NOPTI CPU: 2 UID: 0 PID: 209 Comm: repro_proc_sys_ Not tainted 7.1.0-rc4-00686-g97625979a5d4 PREEMPT(lazy) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014 RIP: 0010:kfree+0x6e/0x510 ... Call Trace: ? __cgroup_bpf_run_filter_sysctl+0x626/0xc30 __cgroup_bpf_run_filter_sysctl+0x74d/0xc30 ? __pfx___cgroup_bpf_run_filter_sysctl+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? __kvmalloc_node_noprof+0x345/0x870 ? proc_sys_call_handler+0x250/0x480 ? srso_return_thunk+0x5/0x5f proc_sys_call_handler+0x3a2/0x480 ? __pfx_proc_sys_call_handler+0x10/0x10 ? srso_return_thunk+0x5/0x5f ? selinux_file_permission+0x39f/0x500 ? srso_return_thunk+0x5/0x5f ? lock_is_held_type+0x9e/0x120 vfs_write+0x98e/0x1000 ... With this fix applied on top of the same test setup, rerunning the reproducer with fail-nth=1 yields no corresponding Oops reports. Fixes: 4508943794ef ("proc: use kvzalloc for our kernel buffer") Cc: stable@vger.kernel.org Reviewed-by: Emil Tsalapatis Reviewed-by: Jiayuan Chen Acked-by: Yonghong Song Signed-off-by: Zilin Guan Signed-off-by: Dawei Feng Link: https://lore.kernel.org/r/20260603105317.944304-3-dawei.feng@seu.edu.cn Signed-off-by: Alexei Starovoitov Signed-off-by: Greg Kroah-Hartman --- kernel/bpf/cgroup.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -1776,7 +1776,7 @@ int __cgroup_bpf_run_filter_sysctl(struc kfree(ctx.cur_val); if (ret == 1 && ctx.new_updated) { - kfree(*buf); + kvfree(*buf); *buf = ctx.new_val; *pcount = ctx.new_len; } else {