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Message-ID: <wxumqnq4u6c3m3oqycvryjghtrrfqn3nbgvrxv2goitprsttdd@i7lilfbyptye>
Date: Mon, 27 Oct 2025 11:14:55 +0100
From: Joel Granados <joel.granados@...nel.org>
To: kernel test robot <lkp@...el.com>
Cc: Kees Cook <kees@...nel.org>, Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, oe-kbuild-all@...ts.linux.dev,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 7/7] sysctl: Wrap do_proc_douintvec with the public
function proc_douintvec_conv
On Wed, Oct 22, 2025 at 05:18:51PM +0800, kernel test robot wrote:
> Hi Joel,
>
> kernel test robot noticed the following build warnings:
>
> [auto build test WARNING on 130e5390ba572bffa687f32ed212dac1105b654a]
>
> url: https://github.com/intel-lab-lkp/linux/commits/Joel-Granados/sysctl-Allow-custom-converters-from-outside-sysctl/20251017-163832
> base: 130e5390ba572bffa687f32ed212dac1105b654a
> patch link: https://lore.kernel.org/r/20251017-jag-sysctl_jiffies-v1-7-175d81dfdf82%40kernel.org
> patch subject: [PATCH 7/7] sysctl: Wrap do_proc_douintvec with the public function proc_douintvec_conv
> config: i386-randconfig-063-20251022 (https://download.01.org/0day-ci/archive/20251022/202510221719.3ggn070M-lkp@intel.com/config)
> compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251022/202510221719.3ggn070M-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202510221719.3ggn070M-lkp@intel.com/
>
> sparse warnings: (new ones prefixed by >>)
> >> kernel/kstack_erase.c:34:56: sparse: sparse: incorrect type in argument 3 (different address spaces) @@ expected void *buffer @@ got void [noderef] __user *buffer @@
> kernel/kstack_erase.c:34:56: sparse: expected void *buffer
> kernel/kstack_erase.c:34:56: sparse: got void [noderef] __user *buffer
This is probably a false positive where the warning was already there
but it moved up in the output (probably due to the function moving up in
the header?)
This made me look a bit more into the issue and I believe that it does
show an issue. Not with the current series, but with commit 0df8bdd5e3b3
("stackleak: move stack_erasing sysctl to stackleak.c"). In this commit
the buffer argument was changed frim void* to void __user*
but in 32927393dc1c ("sysctl: pass kernel pointers to ->proc_handler")
the "__user" was removed. I'll post another patch to fix this up.
Best
> kernel/kstack_erase.c:54:35: sparse: sparse: incorrect type in initializer (incompatible argument 3 (different address spaces)) @@ expected int ( [usertype] *proc_handler )( ... ) @@ got int ( * )( ... ) @@
> kernel/kstack_erase.c:54:35: sparse: expected int ( [usertype] *proc_handler )( ... )
> kernel/kstack_erase.c:54:35: sparse: got int ( * )( ... )
>
> vim +34 kernel/kstack_erase.c
>
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 23
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 24 #ifdef CONFIG_SYSCTL
> 78eb4ea25cd5fd kernel/stackleak.c Joel Granados 2024-07-24 25 static int stack_erasing_sysctl(const struct ctl_table *table, int write,
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 26 void __user *buffer, size_t *lenp, loff_t *ppos)
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 27 {
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 28 int ret = 0;
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 29 int state = !static_branch_unlikely(&stack_erasing_bypass);
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 30 int prev_state = state;
> 0e148d3cca0dc1 kernel/stackleak.c Thomas Weißschuh 2024-05-03 31 struct ctl_table table_copy = *table;
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 32
> 0e148d3cca0dc1 kernel/stackleak.c Thomas Weißschuh 2024-05-03 33 table_copy.data = &state;
> 0e148d3cca0dc1 kernel/stackleak.c Thomas Weißschuh 2024-05-03 @34 ret = proc_dointvec_minmax(&table_copy, write, buffer, lenp, ppos);
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 35 state = !!state;
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 36 if (ret || !write || state == prev_state)
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 37 return ret;
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 38
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 39 if (state)
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 40 static_branch_disable(&stack_erasing_bypass);
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 41 else
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 42 static_branch_enable(&stack_erasing_bypass);
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 43
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 44 pr_warn("stackleak: kernel stack erasing is %s\n",
> 62e9c1e8ecee87 kernel/stackleak.c Thorsten Blum 2024-12-22 45 str_enabled_disabled(state));
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 46 return ret;
> 964c9dff009189 kernel/stackleak.c Alexander Popov 2018-08-17 47 }
> 1751f872cc97f9 kernel/stackleak.c Joel Granados 2025-01-28 48 static const struct ctl_table stackleak_sysctls[] = {
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 49 {
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 50 .procname = "stack_erasing",
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 51 .data = NULL,
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 52 .maxlen = sizeof(int),
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 53 .mode = 0600,
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 54 .proc_handler = stack_erasing_sysctl,
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 55 .extra1 = SYSCTL_ZERO,
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 56 .extra2 = SYSCTL_ONE,
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 57 },
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 58 };
> 0df8bdd5e3b3e5 kernel/stackleak.c Xiaoming Ni 2022-01-21 59
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
--
Joel Granados
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