Re: [PATCH v2] powerpc/kexec: Annotate umem_info members with __counted_by_ptr()

[Sourabh Jain]

On 20/10/26 17:10, Thorsten Blum wrote:
Add __counted_by_ptr() to umem_info::buf and umem_info::ranges to
improve access bounds checking via CONFIG_UBSAN_BOUNDS and
CONFIG_FORTIFY_SOURCE.

In check_realloc_usable_mem(), return early on krealloc() failure and
use sizeof(*buf) when deriving max_entries from the allocation size.

Signed-off-by: Thorsten Blum <b...@kernel.org>
---
Changes in v2:
- Preserve the original pointer/count assignment order (Sourabh Jain)
- v1: https://lore.kernel.org/r/20260730130248.597249-2-thorsten.b...@linux.dev/
[...]
---
  arch/powerpc/kexec/file_load_64.c | 21 +++++++++++----------
  1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kexec/file_load_64.c 
b/arch/powerpc/kexec/file_load_64.c
index bd80c5fb1b1f..7f45493e7c7a 100644
--- a/arch/powerpc/kexec/file_load_64.c
+++ b/arch/powerpc/kexec/file_load_64.c
@@ -34,14 +34,14 @@
  #include <asm/cputhreads.h>
  
  struct umem_info {
-       __be64 *buf;            /* data buffer for usable-memory property */
+       __be64 *buf __counted_by_ptr(max_entries); /* data buffer for 
usable-memory property */
        u32 size;               /* size allocated for the data buffer */
        u32 max_entries;        /* maximum no. of entries */
        u32 idx;                /* index of current entry */
  
  	/* usable memory ranges to look up */
        unsigned int nr_ranges;
-       const struct range *ranges;
+       const struct range *ranges __counted_by_ptr(nr_ranges);
  };
  
  const struct kexec_file_ops * const kexec_file_loaders[] = {
@@ -83,11 +83,12 @@ static __be64 *check_realloc_usable_mem(struct umem_info 
*um_info, int cnt)
  
  	new_size = um_info->size + MEM_RANGE_CHUNK_SZ;
        tbuf = krealloc(um_info->buf, new_size, GFP_KERNEL);
-       if (tbuf) {
-               um_info->buf = tbuf;
-               um_info->size = new_size;
-               um_info->max_entries = (um_info->size / sizeof(u64));
-       }
+       if (!tbuf)
+               return NULL;
+
+       um_info->buf = tbuf;
+       um_info->size = new_size;
+       um_info->max_entries = um_info->size / sizeof(*um_info->buf);

Yeah, it is better to maintain the order. The changes look good to me. 
Feel free to add them.
Reviewed-by: Sourabh Jain <sourabhj...@linux.ibm.com>

  
  	return tbuf;
  }
@@ -288,12 +289,12 @@ static int update_usable_mem_fdt(void *fdt, struct 
crash_mem *usable_mem)
                return -EINVAL;
        }
  
-	um_info.buf  = NULL;
+       um_info.buf = NULL;
        um_info.size = 0;
        um_info.max_entries = 0;
-       um_info.idx  = 0;
+       um_info.idx = 0;
        /* Memory ranges to look up */
-       um_info.ranges = &(usable_mem->ranges[0]);
+       um_info.ranges = usable_mem->ranges;
        um_info.nr_ranges = usable_mem->nr_ranges;
  
  	dn = of_find_node_by_path("/ibm,dynamic-reconfiguration-memory");