On 01/17/23 at 02:03pm, Dan Carpenter wrote:
> Hello Baoquan He,
>
> This static checker warning is related to yesterdays, but more straight
> forward to analyze.
>
> The patch ae5dfc510155: "mm/vmalloc: explicitly identify vm_map_ram
> area when shown in /proc/vmcoreinfo" from Jan 13, 2023, leads to the
> following Smatch static checker warning:
>
> mm/vmalloc.c:4244 s_show()
> error: we previously assumed 'v' could be null (see line 4241)
Thanks a lot, Dan. This is a good catch.
Below change should fix it. There are concerns in the patchset thread
where this patch is carried. I will reply and see if I need repost a new
version, or append below draft patch and post.
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 320e3d77a9dd..a0cec3e27e2c 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4125,10 +4125,11 @@ static int s_show(struct seq_file *m, void *p)
va = list_entry(p, struct vmap_area, list);
- if (!va->vm && (va->flags & VMAP_RAM)) {
- seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n",
- (void *)va->va_start, (void *)va->va_end,
- va->va_end - va->va_start);
+ if (!va->vm) {
+ if (va->flags & VMAP_RAM) {
+ seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n",
+ (void *)va->va_start, (void *)va->va_end,
+ va->va_end - va->va_start);
goto final;
}
>
> mm/vmalloc.c
> 4226 static int s_show(struct seq_file *m, void *p)
> 4227 {
> 4228 struct vmap_area *va;
> 4229 struct vm_struct *v;
> 4230
> 4231 va = list_entry(p, struct vmap_area, list);
> 4232
> 4233 if (!va->vm && (va->flags & VMAP_RAM)) {
> ^^^^^^ ^^^^^^^^^^^^^^^^^^^^
> Assume va->vm is NULL but the VMAP_RAM flag is not set.
>
> 4234 seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n",
> 4235 (void *)va->va_start, (void *)va->va_end,
> 4236 va->va_end - va->va_start);
> 4237
> 4238 goto final;
> 4239 }
> 4240
> 4241 v = va->vm;
> ^^^^^^^^^^
> Assignment
>
> 4242
> 4243 seq_printf(m, "0x%pK-0x%pK %7ld",
> --> 4244 v->addr, v->addr + v->size, v->size);
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Dead.
>
> 4245
> 4246 if (v->caller)
> 4247 seq_printf(m, " %pS", v->caller);
> 4248
>
> regards,
> dan carpenter
>
