mm: cma: fix the name of CMA areas

Patch series "mm: fix the names of general cma and hugetlb cma", v2.

The current code of CMA can only work when users pass a const string as
name parameter.  we need to fix the way to handle names in CMA.  On the
other hand, to avoid name conflicts after enabling CMA_DEBUGFS, each
hugetlb should get a different CMA name.

This patch (of 2):

If users give a name saved in stack, the current code will generate magic
pointer.  if users don't give a name(NULL), kasprintf() will always return
NULL as we are at the early stage.  that means cma_init_reserved_mem()
will return -ENOMEM if users set name parameter as NULL.

[natechancellor@gmail.com: return cma->name directly in cma_get_name]
Link: https://github.com/ClangBuiltLinux/linux/issues/1063
Link: http://lkml.kernel.org/r/20200623015840.621964-1-natechancellor@gmail.com
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Roman Gushchin <guro@fb.com>
Link: http://lkml.kernel.org/r/20200616223131.33828-2-song.bao.hua@hisilicon.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/cma.c b/mm/cma.c
index 3a18f8d..aa2df0b 100644 (file)
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -52,7 +52,7 @@ unsigned long cma_get_size(const struct cma *cma)
 
 const char *cma_get_name(const struct cma *cma)
 {
-       return cma->name ? cma->name : "(undefined)";
+       return cma->name;
 }
 
 static unsigned long cma_bitmap_aligned_mask(const struct cma *cma,
@@ -202,13 +202,12 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
         * subsystems (like slab allocator) are available.
         */
        cma = &cma_areas[cma_area_count];
-       if (name) {
-               cma->name = name;
-       } else {
-               cma->name = kasprintf(GFP_KERNEL, "cma%d\n", cma_area_count);
-               if (!cma->name)
-                       return -ENOMEM;
-       }
+
+       if (name)
+               snprintf(cma->name, CMA_MAX_NAME, name);
+       else
+               snprintf(cma->name, CMA_MAX_NAME,  "cma%d\n", cma_area_count);
+
        cma->base_pfn = PFN_DOWN(base);
        cma->count = size >> PAGE_SHIFT;
        cma->order_per_bit = order_per_bit;

diff --git a/mm/cma.h b/mm/cma.h
index 6698fa6..20f6e24 100644 (file)
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -4,6 +4,8 @@
 
 #include <linux/debugfs.h>
 
+#define CMA_MAX_NAME 64
+
 struct cma {
        unsigned long   base_pfn;
        unsigned long   count;
@@ -15,7 +17,7 @@ struct cma {
        spinlock_t mem_head_lock;
        struct debugfs_u32_array dfs_bitmap;
 #endif
-       const char *name;
+       char name[CMA_MAX_NAME];
 };
 
 extern struct cma cma_areas[MAX_CMA_AREAS];