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authorAl Viro <viro@zeniv.linux.org.uk>2011-03-08 01:25:28 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2011-03-08 02:22:27 -0500
commitdfef6dcd35cb4a251f6322ca9b2c06f0bb1aa1f4 (patch)
tree65e8a25d4ed913658db35c4b97ab0a021c2124eb /fs
parent1858efd471624ecb37e6b5462cab8076f47d1cee (diff)
downloadblackbird-op-linux-dfef6dcd35cb4a251f6322ca9b2c06f0bb1aa1f4.tar.gz
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unfuck proc_sysctl ->d_compare()
a) struct inode is not going to be freed under ->d_compare(); however, the thing PROC_I(inode)->sysctl points to just might. Fortunately, it's enough to make freeing that sucker delayed, provided that we don't step on its ->unregistering, clear the pointer to it in PROC_I(inode) before dropping the reference and check if it's NULL in ->d_compare(). b) I'm not sure that we *can* walk into NULL inode here (we recheck dentry->seq between verifying that it's still hashed / fetching dentry->d_inode and passing it to ->d_compare() and there's no negative hashed dentries in /proc/sys/*), but if we can walk into that, we really should not have ->d_compare() return 0 on it! Said that, I really suspect that this check can be simply killed. Nick? Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs')
-rw-r--r--fs/proc/inode.c8
-rw-r--r--fs/proc/proc_sysctl.c7
2 files changed, 11 insertions, 4 deletions
diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 176ce4cda68a..d6a7ca1fdac5 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -27,6 +27,7 @@
static void proc_evict_inode(struct inode *inode)
{
struct proc_dir_entry *de;
+ struct ctl_table_header *head;
truncate_inode_pages(&inode->i_data, 0);
end_writeback(inode);
@@ -38,8 +39,11 @@ static void proc_evict_inode(struct inode *inode)
de = PROC_I(inode)->pde;
if (de)
pde_put(de);
- if (PROC_I(inode)->sysctl)
- sysctl_head_put(PROC_I(inode)->sysctl);
+ head = PROC_I(inode)->sysctl;
+ if (head) {
+ rcu_assign_pointer(PROC_I(inode)->sysctl, NULL);
+ sysctl_head_put(head);
+ }
}
struct vfsmount *proc_mnt;
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 09a1f92a34ef..8eb2522111c5 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -408,15 +408,18 @@ static int proc_sys_compare(const struct dentry *parent,
const struct dentry *dentry, const struct inode *inode,
unsigned int len, const char *str, const struct qstr *name)
{
+ struct ctl_table_header *head;
/* Although proc doesn't have negative dentries, rcu-walk means
* that inode here can be NULL */
+ /* AV: can it, indeed? */
if (!inode)
- return 0;
+ return 1;
if (name->len != len)
return 1;
if (memcmp(name->name, str, len))
return 1;
- return !sysctl_is_seen(PROC_I(inode)->sysctl);
+ head = rcu_dereference(PROC_I(inode)->sysctl);
+ return !head || !sysctl_is_seen(head);
}
static const struct dentry_operations proc_sys_dentry_operations = {
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