Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues: - [High] The kernel fails to validate the untrusted `meta->nr_subbufs` value from persistent memory against the expected `nr_pages + 1`, leading to arbitrary heap out-of-bounds writes and potential arbitrary kernel memory corruption. -- commit 5ed0ab549782b2ff87e1bd2394abb78b10c4b602 Author: Vincent Donnefort <[email protected]> ring-buffer: Prevent truncation of nr_pages / nr_subbufs Although ring_buffer_per_cpu::nr_pages is defined as unsigned long, it is capped to 32-bits in a few places, limiting the operations possible on a very large buffer. Use unsigned long where appropriate and prevent truncation of values using nr_pages (or nr_subbufs). While at it, subbuf_size must be at least unsigned int. Note that persistent, remote and user-mapped ring buffers are capping the number of pages to 31 bits already, making "int" safe in many places. > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 6089fcc67e2b6..1fcf55e2ca81f 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -1745,7 +1744,7 @@ static void *rb_range_meta(struct trace_buffer *buffer, > int nr_pages, int cpu) > /* Return the start of subbufs given the meta pointer */ > static void *rb_subbufs_from_meta(struct ring_buffer_cpu_meta *meta) > { > - int subbuf_size = meta->subbuf_size; > + unsigned int subbuf_size = meta->subbuf_size; > unsigned long ptr; > > ptr = (unsigned long)meta; [Severity: High] This isn't a bug introduced by this patch, but does the next line in this function perform pointer arithmetic using an unvalidated meta->nr_subbufs? ptr = rb_range_align_subbuf(ptr, subbuf_size, meta->nr_subbufs); Could this yield a corrupted or attacker-controlled subbuf base pointer if meta->nr_subbufs is read from persistent memory without being checked against expected limits? [ ... ] > @@ -1854,13 +1853,13 @@ static bool rb_meta_init(struct trace_buffer *buffer, > int scratch_size) > * must be the same. > */ > static bool rb_cpu_meta_valid(struct ring_buffer_cpu_meta *meta, int cpu, > - struct trace_buffer *buffer, int nr_pages, > + struct trace_buffer *buffer, unsigned long > nr_pages, > unsigned long *subbuf_mask) > { > - int subbuf_size = PAGE_SIZE; > + unsigned long subbuf_size = PAGE_SIZE; > unsigned long buffers_start; > unsigned long buffers_end; > - int i; > + unsigned long i; > > if (!subbuf_mask) > return false; [Severity: High] This isn't a bug introduced by this patch, but is there a risk of an out-of-bounds heap write further down in this function? The subbuf_mask is allocated with nr_pages + 1 bits in rb_range_meta_init(), but later in rb_cpu_meta_valid() operations use the unvalidated meta->nr_subbufs value read from persistent memory: bitmap_clear(subbuf_mask, 0, meta->nr_subbufs); /* * Ensure the meta::buffers array has correct data. The data in each subbufs * are checked later in rb_meta_validate_events(). */ for (i = 0; i < meta->nr_subbufs; i++) { if (meta->buffers[i] < 0 || meta->buffers[i] >= meta->nr_subbufs) { pr_info("Ring buffer boot meta [%d] array out of range\n", cpu); return false; } if (test_bit(meta->buffers[i], subbuf_mask)) { pr_info("Ring buffer boot meta [%d] array has duplicates\n", cpu); return false; } set_bit(meta->buffers[i], subbuf_mask); } If meta->nr_subbufs is larger than nr_pages + 1, could this write out of bounds and corrupt kernel memory? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=3
