Re: [PATCH v3 31/35] lib: add memory allocations report in show_mem()

[Kees Cook]

On Mon, Feb 12, 2024 at 01:39:17PM -0800, Suren Baghdasaryan wrote:
> Include allocations in show_mem reports.
> 
> Signed-off-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> ---
>  include/linux/alloc_tag.h |  2 ++
>  lib/alloc_tag.c           | 38 ++++++++++++++++++++++++++++++++++++++
>  mm/show_mem.c             | 15 +++++++++++++++
>  3 files changed, 55 insertions(+)
> 
> diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h
> index 3fe51e67e231..0a5973c4ad77 100644
> --- a/include/linux/alloc_tag.h
> +++ b/include/linux/alloc_tag.h
> @@ -30,6 +30,8 @@ struct alloc_tag {
>  
>  #ifdef CONFIG_MEM_ALLOC_PROFILING
>  
> +void alloc_tags_show_mem_report(struct seq_buf *s);
> +
>  static inline struct alloc_tag *ct_to_alloc_tag(struct codetag *ct)
>  {
>  	return container_of(ct, struct alloc_tag, ct);
> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
> index 2d5226d9262d..54312c213860 100644
> --- a/lib/alloc_tag.c
> +++ b/lib/alloc_tag.c
> @@ -96,6 +96,44 @@ static const struct seq_operations allocinfo_seq_op = {
>  	.show	= allocinfo_show,
>  };
>  
> +void alloc_tags_show_mem_report(struct seq_buf *s)
> +{
> +	struct codetag_iterator iter;
> +	struct codetag *ct;
> +	struct {
> +		struct codetag		*tag;
> +		size_t			bytes;
> +	} tags[10], n;
> +	unsigned int i, nr = 0;
> +
> +	codetag_lock_module_list(alloc_tag_cttype, true);
> +	iter = codetag_get_ct_iter(alloc_tag_cttype);
> +	while ((ct = codetag_next_ct(&iter))) {
> +		struct alloc_tag_counters counter = alloc_tag_read(ct_to_alloc_tag(ct));
> +
> +		n.tag	= ct;
> +		n.bytes = counter.bytes;
> +
> +		for (i = 0; i < nr; i++)
> +			if (n.bytes > tags[i].bytes)
> +				break;
> +
> +		if (i < ARRAY_SIZE(tags)) {
> +			nr -= nr == ARRAY_SIZE(tags);
> +			memmove(&tags[i + 1],
> +				&tags[i],
> +				sizeof(tags[0]) * (nr - i));
> +			nr++;
> +			tags[i] = n;
> +		}
> +	}
> +
> +	for (i = 0; i < nr; i++)
> +		alloc_tag_to_text(s, tags[i].tag);
> +
> +	codetag_lock_module_list(alloc_tag_cttype, false);
> +}
> +
>  static void __init procfs_init(void)
>  {
>  	proc_create_seq("allocinfo", 0444, NULL, &allocinfo_seq_op);
> diff --git a/mm/show_mem.c b/mm/show_mem.c
> index 8dcfafbd283c..d514c15ca076 100644
> --- a/mm/show_mem.c
> +++ b/mm/show_mem.c
> @@ -12,6 +12,7 @@
>  #include <linux/hugetlb.h>
>  #include <linux/mm.h>
>  #include <linux/mmzone.h>
> +#include <linux/seq_buf.h>
>  #include <linux/swap.h>
>  #include <linux/vmstat.h>
>  
> @@ -423,4 +424,18 @@ void __show_mem(unsigned int filter, nodemask_t *nodemask, int max_zone_idx)
>  #ifdef CONFIG_MEMORY_FAILURE
>  	printk("%lu pages hwpoisoned\n", atomic_long_read(&num_poisoned_pages));
>  #endif
> +#ifdef CONFIG_MEM_ALLOC_PROFILING
> +	{
> +		struct seq_buf s;
> +		char *buf = kmalloc(4096, GFP_ATOMIC);

Why 4096? Maybe use PAGE_SIZE instead?

> +
> +		if (buf) {
> +			printk("Memory allocations:\n");

This needs a printk prefix, or better yet, just use pr_info() or similar.

> +			seq_buf_init(&s, buf, 4096);
> +			alloc_tags_show_mem_report(&s);
> +			printk("%s", buf);

Once a seq_buf "consumes" a char *, please don't use any directly any
more. This should be:

			pr_info("%s", seq_buf_str(s));

Otherwise %NUL termination isn't certain. Very likely, given the use
case here, but let's use good hygiene. :)

> +			kfree(buf);
> +		}
> +	}
> +#endif
>  }
> -- 
> 2.43.0.687.g38aa6559b0-goog
> 

-- 
Kees Cook