Re: [PATCH] Fix blktrace setup 32-bit ioctl on 64-bit kernels

Arnd Bergmann
2007-10-03T15:55:49Z

Here's my counterproposal for the blktrace compat code. It doesn't have
any of the problems I found in your patch obviously, but I haven't tested
it either, so I'm sure you can spot a bug or two in here. Comments?

Jens, I think the best overall solution would be to have a
block/compat_ioctl.c file with all the compat handling for block
devices moved over from fs/compat_ioctl.c, and done in a nicer way.
If you agree, with this approach, I'd volunteer to come up with a
patch.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Index: linux-2.6/block/blktrace.c
===================================================================
--- linux-2.6.orig/block/blktrace.c
+++ linux-2.6/block/blktrace.c
@@ -312,33 +312,26 @@ static struct rchan_callbacks blk_relay_
/*
* Setup everything required to start tracing
*/
-static int blk_trace_setup(struct request_queue *q, struct block_device *bdev,
- char __user *arg)
+static int do_blk_trace_setup(struct request_queue *q, struct block_device *bdev,
+ struct blk_user_trace_setup *buts)
{
- struct blk_user_trace_setup buts;
struct blk_trace *old_bt, *bt = NULL;
struct dentry *dir = NULL;
char b[BDEVNAME_SIZE];
int ret, i;

- if (copy_from_user(&buts, arg, sizeof(buts)))
- return -EFAULT;
-
- if (!buts.buf_size || !buts.buf_nr)
+ if (!buts->buf_size || !buts->buf_nr)
return -EINVAL;

- strcpy(buts.name, bdevname(bdev, b));
+ strcpy(buts->name, bdevname(bdev, b));

/*
* some device names have larger paths - convert the slashes
* to underscores for this to work as expected
*/
- for (i = 0; i < strlen(buts.name); i++)
- if (buts.name[i] == '/')
- buts.name[i] = '_';
-
- if (copy_to_user(arg, &buts, sizeof(buts)))
- return -EFAULT;
+ for (i = 0; i < strlen(buts->name); i++)
+ if (buts->name[i] == '/')
+ buts->name[i] = '_';

ret = -ENOMEM;
bt = kzalloc(sizeof(*bt), GFP_KERNEL);
@@ -350,7 +343,7 @@ static int blk_trace_setup(struct reques
goto err;

ret = -ENOENT;
- dir = blk_create_tree(buts.name);
+ dir = blk_create_tree(buts->name);
if (!dir)
goto err;

@@ -363,20 +356,21 @@ static int blk_trace_setup(struct reques
if (!bt->dropped_file)
goto err;

- bt->rchan = relay_open("trace", dir, buts.buf_size, buts.buf_nr, &blk_relay_callbacks, bt);
+ bt->rchan = relay_open("trace", dir, buts->buf_size,
+ buts->buf_nr, &blk_relay_callbacks, bt);
if (!bt->rchan)
goto err;

- bt->act_mask = buts.act_mask;
+ bt->act_mask = buts->act_mask;
if (!bt->act_mask)
bt->act_mask = (u16) -1;

- bt->start_lba = buts.start_lba;
- bt->end_lba = buts.end_lba;
+ bt->start_lba = buts->start_lba;
+ bt->end_lba = buts->end_lba;
if (!bt->end_lba)
bt->end_lba = -1ULL;

- bt->pid = buts.pid;
+ bt->pid = buts->pid;
bt->trace_state = Blktrace_setup;

ret = -EBUSY;
@@ -401,6 +395,26 @@ err:
return ret;
}

+static int blk_trace_setup(struct request_queue *q, struct block_device *bdev,
+ char __user *arg)
+{
+ struct blk_user_trace_setup buts;
+ int ret;
+
+ ret = copy_from_user(&buts, arg, sizeof(buts));
+ if (ret)
+ return -EFAULT;
+
+ ret = do_blk_trace_setup(q, bdev, &buts);
+ if (ret)
+ return ret;
+
+ if (copy_to_user(arg, &buts, sizeof(buts)))
+ return -EFAULT;
+
+ return 0;
+}
+
static int blk_trace_startstop(struct request_queue *q, int start)
{
struct blk_trace *bt;
@@ -474,6 +488,53 @@ int blk_trace_ioctl(struct block_device
return ret;
}

+#if defined(CONFIG_COMPAT)
+static inline int compat_blk_trace_setup(struct request_queue *q,
+ struct block_device *bdev, char __user *arg)
+{
+ struct blk_user_trace_setup buts;
+ struct compat_blk_user_trace_setup cbuts;
+ int ret;
+
+ if (copy_from_user(&cbuts, arg, sizeof(cbuts)))
+ return -EFAULT;
+
+ buts = (struct blk_user_trace_setup) {
+ .act_mask = cbuts.act_mask,
+ .buf_size = cbuts.buf_size,
+ .buf_nr = cbuts.buf_nr,
+ .start_lba = cbuts.start_lba,
+ .end_lba = cbuts.end_lba,
+ .pid = cbuts.pid,
+ };
+ memcpy(&buts.name, &cbuts.name, 32);
+
+ mutex_lock(&bdev->bd_mutex);
+ ret = do_blk_trace_setup(q, bdev, &buts);
+ mutex_unlock(&bdev->bd_mutex);
+ if (ret)
+ return ret;
+
+ if (copy_to_user(arg, &buts.name, 32))
+ return -EFAULT;
+
+ return 0;
+}
+
+int compat_blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg)
+{
+
+ if (cmd == BLKTRACESETUP32) {
+ struct request_queue *q = bdev_get_queue(bdev);
+ if (!q)
+ return -ENXIO;
+ return compat_blk_trace_setup(q, bdev, arg);
+ }
+
+ return blk_trace_ioctl(bdev, cmd, arg);
+}
+#endif
+
/**
* blk_trace_shutdown: - stop and cleanup trace structures
* @q: the request queue associated with the device
Index: linux-2.6/block/ioctl.c
===================================================================
--- linux-2.6.orig/block/ioctl.c
+++ linux-2.6/block/ioctl.c
@@ -290,14 +290,25 @@ int blkdev_ioctl(struct inode *inode, st
ENOIOCTLCMD for unknown ioctls. */
long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
{
+ int ret = -ENOIOCTLCMD;
+#ifdef CONFIG_COMPAT
struct block_device *bdev = file->f_path.dentry->d_inode->i_bdev;
struct gendisk *disk = bdev->bd_disk;
- int ret = -ENOIOCTLCMD;
+
+ switch (cmd) {
+ case BLKTRACESTART:
+ case BLKTRACESTOP:
+ case BLKTRACESETUP32:
+ case BLKTRACETEARDOWN:
+ return blk_trace_ioctl(bdev, cmd, (char __user *) arg);
+ }
+
if (disk->fops->compat_ioctl) {
lock_kernel();
ret = disk->fops->compat_ioctl(file, cmd, arg);
unlock_kernel();
}
+#endif
return ret;
}

Index: linux-2.6/include/linux/blktrace_api.h
===================================================================
--- linux-2.6.orig/include/linux/blktrace_api.h
+++ linux-2.6/include/linux/blktrace_api.h
@@ -142,6 +142,23 @@ struct blk_user_trace_setup {
u32 pid;
};

+#ifdef __KERNEL__
+#include <linux/compat.h>
+
+#ifdef CONFIG_COMPAT
+struct compat_blk_user_trace_setup {
+ char name[32];
+ u16 act_mask;
+ u32 buf_size;
+ u32 buf_nr;
+ compat_u64 start_lba;
+ compat_u64 end_lba;
+ u32 pid;
+};
+#define BLKTRACESETUP32 _IOWR(0x12,115,struct compat_blk_user_trace_setup)
+
+#endif /* CONFIG_COMPAT */
+
#if defined(CONFIG_BLK_DEV_IO_TRACE)
extern int blk_trace_ioctl(struct block_device *, unsigned, char __user *);
extern void blk_trace_shutdown(struct request_queue *);
@@ -287,5 +304,6 @@ static inline void blk_add_trace_remap(s
#define blk_add_trace_pdu_int(q, what, bio, pdu) do { } while (0)
#define blk_add_trace_remap(q, bio, dev, f, t) do {} while (0)
#endif /* CONFIG_BLK_DEV_IO_TRACE */
+#endif /* __KERNEL__ */

#endif
Index: linux-2.6/fs/compat_ioctl.c
===================================================================
--- linux-2.6.orig/fs/compat_ioctl.c
+++ linux-2.6/fs/compat_ioctl.c
@@ -2553,10 +2553,6 @@ COMPATIBLE_IOCTL(BLKRRPART)
COMPATIBLE_IOCTL(BLKFLSBUF)
COMPATIBLE_IOCTL(BLKSECTSET)
COMPATIBLE_IOCTL(BLKSSZGET)
-COMPATIBLE_IOCTL(BLKTRACESTART)
-COMPATIBLE_IOCTL(BLKTRACESTOP)
-COMPATIBLE_IOCTL(BLKTRACESETUP)
-COMPATIBLE_IOCTL(BLKTRACETEARDOWN)
ULONG_IOCTL(BLKRASET)
ULONG_IOCTL(BLKFRASET)
#endif