sysfs: only access bin file vm_ops with the active lock

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@aristanetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 26 insertions, 16 deletions

diff --git a/fs/sysfs/bin.c b/fs/sysfs/bin.c
index d31d7b7d5426..a4759833d62d 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;