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    Subject[RFC 4/5] BKL: use no BKL in llseek
    Date
    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@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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