Commit a2b992c8 authored by Jakub Kicinski's avatar Jakub Kicinski Committed by David S. Miller
Browse files

debugfs: make sure we can remove u32_array files cleanly 



debugfs_create_u32_array() allocates a small structure to wrap
the data and size information about the array. If users ever
try to remove the file this leads to a leak since nothing ever
frees this wrapper.

That said there are no upstream users of debugfs_create_u32_array()
that'd remove a u32 array file (we only have one u32 array user in
CMA), so there is no real bug here.

Make callers pass a wrapper they allocated. This way the lifetime
management of the wrapper is on the caller, and we can avoid the
potential leak in debugfs.

CC: Chucheng Luo <luochucheng@vivo.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8fb49c01

Documentation/filesystems/debugfs.rst

+8 −4
Original line number Diff line number Diff line
@@ -185,13 +185,17 @@ byte offsets over a base for the register block. 


If you want to dump an u32 array in debugfs, you can create file with::



    struct debugfs_u32_array {

	u32 *array;

	u32 n_elements;

    };



    void debugfs_create_u32_array(const char *name, umode_t mode,

			struct dentry *parent,

			u32 *array, u32 elements);

			struct debugfs_u32_array *array);



The "array" argument provides data, and the "elements" argument is

the number of elements in the array. Note: Once array is created its

size can not be changed.

The "array" argument wraps a pointer to the array's data and the number

of its elements. Note: Once array is created its size can not be changed.



There is a helper function to create device related seq_file::

fs/debugfs/file.c

+7 −20
Original line number Diff line number Diff line
@@ -918,11 +918,6 @@ struct dentry *debugfs_create_blob(const char *name, umode_t mode, 
}

EXPORT_SYMBOL_GPL(debugfs_create_blob);



struct array_data {

	void *array;

	u32 elements;

};



static size_t u32_format_array(char *buf, size_t bufsize,

			       u32 *array, int array_size)

{
@@ -943,8 +938,8 @@ static size_t u32_format_array(char *buf, size_t bufsize, 


static int u32_array_open(struct inode *inode, struct file *file)

{

	struct array_data *data = inode->i_private;

	int size, elements = data->elements;

	struct debugfs_u32_array *data = inode->i_private;

	int size, elements = data->n_elements;

	char *buf;



	/*
@@ -959,7 +954,7 @@ static int u32_array_open(struct inode *inode, struct file *file) 
	buf[size] = 0;



	file->private_data = buf;

	u32_format_array(buf, size, data->array, data->elements);

	u32_format_array(buf, size, data->array, data->n_elements);



	return nonseekable_open(inode, file);

}
@@ -996,8 +991,7 @@ static const struct file_operations u32_array_fops = { 
 * @parent: a pointer to the parent dentry for this file.  This should be a

 *          directory dentry if set.  If this parameter is %NULL, then the

 *          file will be created in the root of the debugfs filesystem.

 * @array: u32 array that provides data.

 * @elements: total number of elements in the array.

 * @array: wrapper struct containing data pointer and size of the array.

 *

 * This function creates a file in debugfs with the given name that exports

 * @array as data. If the @mode variable is so set it can be read from.
@@ -1005,17 +999,10 @@ static const struct file_operations u32_array_fops = { 
 * Once array is created its size can not be changed.

 */

void debugfs_create_u32_array(const char *name, umode_t mode,

			      struct dentry *parent, u32 *array, u32 elements)

			      struct dentry *parent,

			      struct debugfs_u32_array *array)

{

	struct array_data *data = kmalloc(sizeof(*data), GFP_KERNEL);



	if (data == NULL)

		return;



	data->array = array;

	data->elements = elements;



	debugfs_create_file_unsafe(name, mode, parent, data, &u32_array_fops);

	debugfs_create_file_unsafe(name, mode, parent, array, &u32_array_fops);

}

EXPORT_SYMBOL_GPL(debugfs_create_u32_array);

include/linux/debugfs.h

+9 −3
Original line number Diff line number Diff line
@@ -38,6 +38,11 @@ struct debugfs_regset32 { 
	struct device *dev;	/* Optional device for Runtime PM */

};



struct debugfs_u32_array {

	u32 *array;

	u32 n_elements;

};



extern struct dentry *arch_debugfs_dir;



#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt)		\
@@ -136,7 +141,8 @@ void debugfs_print_regs32(struct seq_file *s, const struct debugfs_reg32 *regs, 
			  int nregs, void __iomem *base, char *prefix);



void debugfs_create_u32_array(const char *name, umode_t mode,

			      struct dentry *parent, u32 *array, u32 elements);

			      struct dentry *parent,

			      struct debugfs_u32_array *array);



struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,

					   struct dentry *parent,
@@ -316,8 +322,8 @@ static inline bool debugfs_initialized(void) 
}



static inline void debugfs_create_u32_array(const char *name, umode_t mode,

					    struct dentry *parent, u32 *array,

					    u32 elements)

					    struct dentry *parent,

					    struct debugfs_u32_array *array)

{

}

mm/cma.h

+3 −0
Original line number Diff line number Diff line
@@ -2,6 +2,8 @@ 
#ifndef __MM_CMA_H__

#define __MM_CMA_H__



#include <linux/debugfs.h>



struct cma {

	unsigned long   base_pfn;

	unsigned long   count;
@@ -11,6 +13,7 @@ struct cma { 
#ifdef CONFIG_CMA_DEBUGFS

	struct hlist_head mem_head;

	spinlock_t mem_head_lock;

	struct debugfs_u32_array dfs_bitmap;

#endif

	const char *name;

};

mm/cma_debug.c

+4 −3
Original line number Diff line number Diff line
@@ -164,7 +164,6 @@ static void cma_debugfs_add_one(struct cma *cma, struct dentry *root_dentry) 
{

	struct dentry *tmp;

	char name[16];

	int u32s;



	scnprintf(name, sizeof(name), "cma-%s", cma->name);
@@ -180,8 +179,10 @@ static void cma_debugfs_add_one(struct cma *cma, struct dentry *root_dentry) 
	debugfs_create_file("used", 0444, tmp, cma, &cma_used_fops);

	debugfs_create_file("maxchunk", 0444, tmp, cma, &cma_maxchunk_fops);



	u32s = DIV_ROUND_UP(cma_bitmap_maxno(cma), BITS_PER_BYTE * sizeof(u32));

	debugfs_create_u32_array("bitmap", 0444, tmp, (u32 *)cma->bitmap, u32s);

	cma->dfs_bitmap.array = (u32 *)cma->bitmap;

	cma->dfs_bitmap.n_elements = DIV_ROUND_UP(cma_bitmap_maxno(cma),

						  BITS_PER_BYTE * sizeof(u32));

	debugfs_create_u32_array("bitmap", 0444, tmp, &cma->dfs_bitmap);

}



static int __init cma_debugfs_init(void)