AuxXxilium/linux_dsm_epyc7002
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Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

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Pull sysctl fix from Eric Biederman:
 "A rather embarassing and hard to hit bug was merged into 4.11-rc1.

  Andrei Vagin tracked this bug now and after some staring at the code
  I came up with a fix"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  proc: Fix proc_sys_prune_dcache to hold a sb reference
This commit is contained in:
Linus Torvalds 2017-07-12 19:43:20 -07:00
commit 4ca6df1348
3 changed files with 32 additions and 15 deletions
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2
fs/proc/internal.h
View File

@ -67,7 +67,7 @@ struct proc_inode {
struct proc_dir_entry *pde; struct proc_dir_entry *pde;
struct ctl_table_header *sysctl; struct ctl_table_header *sysctl;
struct ctl_table *sysctl_entry; struct ctl_table *sysctl_entry;
struct list_head sysctl_inodes; struct hlist_node sysctl_inodes;
const struct proc_ns_operations *ns_ops; const struct proc_ns_operations *ns_ops;
struct inode vfs_inode; struct inode vfs_inode;
}; };

43
fs/proc/proc_sysctl.c
View File

@ -191,7 +191,7 @@ static void init_header(struct ctl_table_header *head,
head->set = set; head->set = set;
head->parent = NULL; head->parent = NULL;
head->node = node; head->node = node;
INIT_LIST_HEAD(&head->inodes); INIT_HLIST_HEAD(&head->inodes);
if (node) { if (node) {
struct ctl_table *entry; struct ctl_table *entry;
for (entry = table; entry->procname; entry++, node++) for (entry = table; entry->procname; entry++, node++)
@ -261,25 +261,42 @@ static void unuse_table(struct ctl_table_header *p)
complete(p->unregistering); complete(p->unregistering);
} }
/* called under sysctl_lock */
static void proc_sys_prune_dcache(struct ctl_table_header *head) static void proc_sys_prune_dcache(struct ctl_table_header *head)
{ {
struct inode *inode, *prev = NULL; struct inode *inode;
struct proc_inode *ei; struct proc_inode *ei;
struct hlist_node *node;
struct super_block *sb;
rcu_read_lock(); rcu_read_lock();
list_for_each_entry_rcu(ei, &head->inodes, sysctl_inodes) { for (;;) {
inode = igrab(&ei->vfs_inode); node = hlist_first_rcu(&head->inodes);
if (inode) { if (!node)
rcu_read_unlock(); break;
iput(prev); ei = hlist_entry(node, struct proc_inode, sysctl_inodes);
prev = inode; spin_lock(&sysctl_lock);
d_prune_aliases(inode); hlist_del_init_rcu(&ei->sysctl_inodes);
spin_unlock(&sysctl_lock);
inode = &ei->vfs_inode;
sb = inode->i_sb;
if (!atomic_inc_not_zero(&sb->s_active))
continue;
inode = igrab(inode);
rcu_read_unlock();
if (unlikely(!inode)) {
deactivate_super(sb);
rcu_read_lock(); rcu_read_lock();
continue;
} }
d_prune_aliases(inode);
iput(inode);
deactivate_super(sb);
rcu_read_lock();
} }
rcu_read_unlock(); rcu_read_unlock();
iput(prev);
} }
/* called under sysctl_lock, will reacquire if has to wait */ /* called under sysctl_lock, will reacquire if has to wait */
@ -461,7 +478,7 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
} }
ei->sysctl = head; ei->sysctl = head;
ei->sysctl_entry = table; ei->sysctl_entry = table;
list_add_rcu(&ei->sysctl_inodes, &head->inodes); hlist_add_head_rcu(&ei->sysctl_inodes, &head->inodes);
head->count++; head->count++;
spin_unlock(&sysctl_lock); spin_unlock(&sysctl_lock);
@ -489,7 +506,7 @@ static struct inode *proc_sys_make_inode(struct super_block *sb,
void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head) void proc_sys_evict_inode(struct inode *inode, struct ctl_table_header *head)
{ {
spin_lock(&sysctl_lock); spin_lock(&sysctl_lock);
list_del_rcu(&PROC_I(inode)->sysctl_inodes); hlist_del_init_rcu(&PROC_I(inode)->sysctl_inodes);
if (!--head->count) if (!--head->count)
kfree_rcu(head, rcu); kfree_rcu(head, rcu);
spin_unlock(&sysctl_lock); spin_unlock(&sysctl_lock);

2
include/linux/sysctl.h
View File

@ -143,7 +143,7 @@ struct ctl_table_header
struct ctl_table_set *set; struct ctl_table_set *set;
struct ctl_dir *parent; struct ctl_dir *parent;
struct ctl_node *node; struct ctl_node *node;
struct list_head inodes; /* head for proc_inode->sysctl_inodes */ struct hlist_head inodes; /* head for proc_inode->sysctl_inodes */
}; };
struct ctl_dir { struct ctl_dir {