[PATCH 21/31] sysfs: only access bin file vm_ops with the active lock

From: Greg Kroah-Hartman
Date: Fri Oct 22 2010 - 14:26:20 EST


From: Eric W. Biederman <ebiederm@xxxxxxxxxxxxxxxxxx>

bb->vm_ops is a cached copy of the vm_ops of the underlying
sysfs bin file, which means that after sysfs_bin_remove_file
completes it is only longer valid to deference bb->vm_ops.

So move all of the tests of bb->vm_ops inside of where
we hold the sysfs active lock.

Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
fs/sysfs/bin.c | 42 ++++++++++++++++++++++++++----------------
1 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index d31d7b7..a475983 100644
--- a/fs/sysfs/bin.c
+++ b/fs/sysfs/bin.c
@@ -179,13 +179,14 @@ static void bin_vma_open(struct vm_area_struct *vma)
struct bin_buffer *bb = file->private_data;
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;

- if (!bb->vm_ops || !bb->vm_ops->open)
+ if (!bb->vm_ops)
return;

if (!sysfs_get_active(attr_sd))
return;

- bb->vm_ops->open(vma);
+ if (bb->vm_ops->open)
+ bb->vm_ops->open(vma);

sysfs_put_active(attr_sd);
}
@@ -197,13 +198,15 @@ static int bin_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
int ret;

- if (!bb->vm_ops || !bb->vm_ops->fault)
+ if (!bb->vm_ops)
return VM_FAULT_SIGBUS;

if (!sysfs_get_active(attr_sd))
return VM_FAULT_SIGBUS;

- ret = bb->vm_ops->fault(vma, vmf);
+ ret = VM_FAULT_SIGBUS;
+ if (bb->vm_ops->fault)
+ ret = bb->vm_ops->fault(vma, vmf);

sysfs_put_active(attr_sd);
return ret;
@@ -219,13 +222,12 @@ static int bin_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
if (!bb->vm_ops)
return VM_FAULT_SIGBUS;

- if (!bb->vm_ops->page_mkwrite)
- return 0;
-
if (!sysfs_get_active(attr_sd))
return VM_FAULT_SIGBUS;

- ret = bb->vm_ops->page_mkwrite(vma, vmf);
+ ret = 0;
+ if (bb->vm_ops->page_mkwrite)
+ ret = bb->vm_ops->page_mkwrite(vma, vmf);

sysfs_put_active(attr_sd);
return ret;
@@ -239,13 +241,15 @@ static int bin_access(struct vm_area_struct *vma, unsigned long addr,
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
int ret;

- if (!bb->vm_ops || !bb->vm_ops->access)
+ if (!bb->vm_ops)
return -EINVAL;

if (!sysfs_get_active(attr_sd))
return -EINVAL;

- ret = bb->vm_ops->access(vma, addr, buf, len, write);
+ ret = -EINVAL;
+ if (bb->vm_ops->access)
+ ret = bb->vm_ops->access(vma, addr, buf, len, write);

sysfs_put_active(attr_sd);
return ret;
@@ -259,13 +263,15 @@ static int bin_set_policy(struct vm_area_struct *vma, struct mempolicy *new)
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
int ret;

- if (!bb->vm_ops || !bb->vm_ops->set_policy)
+ if (!bb->vm_ops)
return 0;

if (!sysfs_get_active(attr_sd))
return -EINVAL;

- ret = bb->vm_ops->set_policy(vma, new);
+ ret = 0;
+ if (bb->vm_ops->set_policy)
+ ret = bb->vm_ops->set_policy(vma, new);

sysfs_put_active(attr_sd);
return ret;
@@ -279,13 +285,15 @@ static struct mempolicy *bin_get_policy(struct vm_area_struct *vma,
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
struct mempolicy *pol;

- if (!bb->vm_ops || !bb->vm_ops->get_policy)
+ if (!bb->vm_ops)
return vma->vm_policy;

if (!sysfs_get_active(attr_sd))
return vma->vm_policy;

- pol = bb->vm_ops->get_policy(vma, addr);
+ pol = vma->vm_policy;
+ if (bb->vm_ops->get_policy)
+ pol = bb->vm_ops->get_policy(vma, addr);

sysfs_put_active(attr_sd);
return pol;
@@ -299,13 +307,15 @@ static int bin_migrate(struct vm_area_struct *vma, const nodemask_t *from,
struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata;
int ret;

- if (!bb->vm_ops || !bb->vm_ops->migrate)
+ if (!bb->vm_ops)
return 0;

if (!sysfs_get_active(attr_sd))
return 0;

- ret = bb->vm_ops->migrate(vma, from, to, flags);
+ ret = 0;
+ if (bb->vm_ops->migrate)
+ ret = bb->vm_ops->migrate(vma, from, to, flags);

sysfs_put_active(attr_sd);
return ret;
--
1.7.2

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