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From: Arnd Bergmann on 2 Jun 2010 20:20
We have shown that the BKL in default_llseek and other
llseek operations never protects against concurrent access
from another function:

* Most drivers never access f_pos
* Most drivers that access f_pos have their own
llseek function
* Those drivers that use default_llseek and still
access f_pos from outside do so without taking the BKL.
* No file system uses default_llseek.

Signed-off-by: Arnd Bergmann <arnd(a)arndb.de>
---
drivers/pnp/isapnp/proc.c | 6 +++---
drivers/usb/core/inode.c | 1 -
drivers/zorro/proc.c | 6 +++---
fs/read_write.c | 4 ++--
4 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/pnp/isapnp/proc.c b/drivers/pnp/isapnp/proc.c
index 3f94eda..cc22c7c 100644
--- a/drivers/pnp/isapnp/proc.c
+++ b/drivers/pnp/isapnp/proc.c
@@ -32,7 +32,7 @@ static loff_t isapnp_proc_bus_lseek(struct file *file, loff_t off, int whence)
{
loff_t new = -1;

- lock_kernel();
+ mutex_lock(&file->f_dentry->d_inode->i_mutex);
switch (whence) {
case 0:
new = off;
@@ -45,10 +45,10 @@ static loff_t isapnp_proc_bus_lseek(struct file *file, loff_t off, int whence)
break;
}
if (new < 0 || new > 256) {
- unlock_kernel();
+ mutex_unlock(&file->f_dentry->d_inode->i_mutex);
return -EINVAL;
}
- unlock_kernel();
+ mutex_unlock(&file->f_dentry->d_inode->i_mutex);
return (file->f_pos = new);
}

diff --git a/drivers/usb/core/inode.c b/drivers/usb/core/inode.c
index 1a27618..70b1d42 100644
--- a/drivers/usb/core/inode.c
+++ b/drivers/usb/core/inode.c
@@ -39,7 +39,6 @@
#include <linux/parser.h>
#include <linux/notifier.h>
#include <linux/seq_file.h>
-#include <linux/smp_lock.h>
#include <linux/usb/hcd.h>
#include <asm/byteorder.h>
#include "usb.h"
diff --git a/drivers/zorro/proc.c b/drivers/zorro/proc.c
index 3c7046d..8e4c505 100644
--- a/drivers/zorro/proc.c
+++ b/drivers/zorro/proc.c
@@ -23,7 +23,7 @@ proc_bus_zorro_lseek(struct file *file, loff_t off, int whence)
{
loff_t new = -1;

- lock_kernel();
+ mutex_lock(&file->f_dentry->d_inode->i_mutex);
switch (whence) {
case 0:
new = off;
@@ -36,10 +36,10 @@ proc_bus_zorro_lseek(struct file *file, loff_t off, int whence)
break;
}
if (new < 0 || new > sizeof(struct ConfigDev)) {
- unlock_kernel();
+ mutex_unlock(&file->f_dentry->d_inode->i_mutex);
return -EINVAL;
}
- unlock_kernel();
+ mutex_unlock(&file->f_dentry->d_inode->i_mutex);
return (file->f_pos = new);
}

diff --git a/fs/read_write.c b/fs/read_write.c
index 9c04852..31c0be7 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -124,7 +124,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
{
loff_t retval;

- lock_kernel();
+ mutex_lock(&file->f_dentry->d_inode->i_mutex);
switch (origin) {
case SEEK_END:
offset += i_size_read(file->f_path.dentry->d_inode);
@@ -145,7 +145,7 @@ loff_t default_llseek(struct file *file, loff_t offset, int origin)
retval = offset;
}
out:
- unlock_kernel();
+ mutex_unlock(&file->f_dentry->d_inode->i_mutex);
return retval;
}
EXPORT_SYMBOL(default_llseek);
--
1.7.0.4

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Prev: [RFC 3/5] BKL: do not take BKL in do_coredump
Next: [RFC 5/5] BKL: introduce CONFIG_BKL.