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alloc_tag: fix rw permission issue when handling boot parameter 

Boot parameters prefixed with "sysctl." are processed during the final
stage of system initialization via kernel_init()-> do_sysctl_args().  When
CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled, the sysctl.vm.mem_profiling
entry is not writable and will cause a warning.

Before run_init_process(), system initialization executes in kernel thread
context.  Use current->mm to distinguish sysctl writes during
do_sysctl_args() from user-space triggered ones.

And when the proc_handler is from do_sysctl_args(), always return success
because the same value was already set by setup_early_mem_profiling() and
this eliminates a permission denied warning.

Link: https://lkml.kernel.org/r/20260115031536.164254-1-ranxiaokai627@163.com
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Suggested-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
master
Ran Xiaokai 2026-01-15 03:15:36 +00:00 committed by Andrew Morton
parent d468d8f86d
commit 77bcee8d40
1 changed files with 16 additions and 6 deletions
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22
lib/alloc_tag.c
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@ -776,8 +776,22 @@ EXPORT_SYMBOL(page_alloc_tagging_ops);
static int proc_mem_profiling_handler(const struct ctl_table *table, int write,
void *buffer, size_t *lenp, loff_t *ppos)
{
if (!mem_profiling_support && write)
return -EINVAL;
if (write) {
/*
* Call from do_sysctl_args() which is a no-op since the same
* value was already set by setup_early_mem_profiling.
* Return success to avoid warnings from do_sysctl_args().
*/
if (!current->mm)
return 0;
#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
/* User can't toggle profiling while debugging */
return -EACCES;
#endif
if (!mem_profiling_support)
return -EINVAL;
}
return proc_do_static_key(table, write, buffer, lenp, ppos);
}
@ -787,11 +801,7 @@ static const struct ctl_table memory_allocation_profiling_sysctls[] = {
{
.procname = "mem_profiling",
.data = &mem_alloc_profiling_key,
#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
.mode = 0444,
#else
.mode = 0644,
#endif
.proc_handler = proc_mem_profiling_handler,
},
};