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

Kees Cook
2024-02-13T00:10:07Z

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@linux.dev>
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> ---
> 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