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qnx4: Extract dir entry filename processing into helper

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Both dir.c and namei.c need to perform the same work to figure out a
directory entry's name and size. Extract this into a helper for use
in the next patch.

Acked-by: Anders Larsen <al@alarsen.net>
Link: https://lore.kernel.org/r/20231130205120.3642477-1-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook 2023-11-30 12:51:18 -08:00
parent ac7110d883
commit 53853995c6
2 changed files with 67 additions and 45 deletions
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52
fs/qnx4/dir.c
View File

@ -15,43 +15,6 @@
#include <linux/buffer_head.h>
#include "qnx4.h"
/*
* A qnx4 directory entry is an inode entry or link info
* depending on the status field in the last byte. The
* first byte is where the name start either way, and a
* zero means it's empty.
*
* Also, due to a bug in gcc, we don't want to use the
* real (differently sized) name arrays in the inode and
* link entries, but always the 'de_name[]' one in the
* fake struct entry.
*
* See
*
* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
*
* for details, but basically gcc will take the size of the
* 'name' array from one of the used union entries randomly.
*
* This use of 'de_name[]' (48 bytes) avoids the false positive
* warnings that would happen if gcc decides to use 'inode.di_name'
* (16 bytes) even when the pointer and size were to come from
* 'link.dl_name' (48 bytes).
*
* In all cases the actual name pointer itself is the same, it's
* only the gcc internal 'what is the size of this field' logic
* that can get confused.
*/
union qnx4_directory_entry {
struct {
const char de_name[48];
u8 de_pad[15];
u8 de_status;
};
struct qnx4_inode_entry inode;
struct qnx4_link_info link;
};
static int qnx4_readdir(struct file *file, struct dir_context *ctx)
{
struct inode *inode = file_inode(file);
@ -74,26 +37,25 @@ static int qnx4_readdir(struct file *file, struct dir_context *ctx)
ix = (ctx->pos >> QNX4_DIR_ENTRY_SIZE_BITS) % QNX4_INODES_PER_BLOCK;
for (; ix < QNX4_INODES_PER_BLOCK; ix++, ctx->pos += QNX4_DIR_ENTRY_SIZE) {
union qnx4_directory_entry *de;
const char *fname;
offset = ix * QNX4_DIR_ENTRY_SIZE;
de = (union qnx4_directory_entry *) (bh->b_data + offset);
if (!de->de_name[0])
continue;
if (!(de->de_status & (QNX4_FILE_USED|QNX4_FILE_LINK)))
fname = get_entry_fname(de, &size);
if (!fname)
continue;
if (!(de->de_status & QNX4_FILE_LINK)) {
size = sizeof(de->inode.di_fname);
ino = blknum * QNX4_INODES_PER_BLOCK + ix - 1;
} else {
size = sizeof(de->link.dl_fname);
ino = ( le32_to_cpu(de->link.dl_inode_blk) - 1 ) *
QNX4_INODES_PER_BLOCK +
de->link.dl_inode_ndx;
}
size = strnlen(de->de_name, size);
QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, name));
if (!dir_emit(ctx, de->de_name, size, ino, DT_UNKNOWN)) {
QNX4DEBUG((KERN_INFO "qnx4_readdir:%.*s\n", size, fname));
if (!dir_emit(ctx, fname, size, ino, DT_UNKNOWN)) {
brelse(bh);
return 0;
}

60
fs/qnx4/qnx4.h
View File

@ -44,3 +44,63 @@ static inline struct qnx4_inode_entry *qnx4_raw_inode(struct inode *inode)
{
return &qnx4_i(inode)->raw;
}
/*
* A qnx4 directory entry is an inode entry or link info
* depending on the status field in the last byte. The
* first byte is where the name start either way, and a
* zero means it's empty.
*
* Also, due to a bug in gcc, we don't want to use the
* real (differently sized) name arrays in the inode and
* link entries, but always the 'de_name[]' one in the
* fake struct entry.
*
* See
*
* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
*
* for details, but basically gcc will take the size of the
* 'name' array from one of the used union entries randomly.
*
* This use of 'de_name[]' (48 bytes) avoids the false positive
* warnings that would happen if gcc decides to use 'inode.di_name'
* (16 bytes) even when the pointer and size were to come from
* 'link.dl_name' (48 bytes).
*
* In all cases the actual name pointer itself is the same, it's
* only the gcc internal 'what is the size of this field' logic
* that can get confused.
*/
union qnx4_directory_entry {
struct {
const char de_name[48];
u8 de_pad[15];
u8 de_status;
};
struct qnx4_inode_entry inode;
struct qnx4_link_info link;
};
static inline const char *get_entry_fname(union qnx4_directory_entry *de,
int *size)
{
/* Make sure the status byte is in the same place for all structs. */
BUILD_BUG_ON(offsetof(struct qnx4_inode_entry, di_status) !=
offsetof(struct qnx4_link_info, dl_status));
BUILD_BUG_ON(offsetof(struct qnx4_inode_entry, di_status) !=
offsetof(union qnx4_directory_entry, de_status));
if (!de->de_name[0])
return NULL;
if (!(de->de_status & (QNX4_FILE_USED|QNX4_FILE_LINK)))
return NULL;
if (!(de->de_status & QNX4_FILE_LINK))
*size = sizeof(de->inode.di_fname);
else
*size = sizeof(de->link.dl_fname);
*size = strnlen(de->de_name, *size);
return de->de_name;
}