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authorSteven Rostedt <rostedt@goodmis.org>2006-03-26 01:36:55 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-26 08:56:53 -0800
commit64a07bd82ed526d813b64b0957543eef55bdf9c0 (patch)
tree451586526696bc4a80d8a9f4c50460ae2d4e92eb /fs/proc/generic.c
parentcd7b24bb1891a10ee25168a912ff2304a9571d23 (diff)
[PATCH] protect remove_proc_entry
It has been discovered that the remove_proc_entry has a race in the removing of entries in the proc file system that are siblings. There's no protection around the traversing and removing of elements that belong in the same subdirectory. This subdirectory list is protected in other areas by the BKL. So the BKL was at first used to protect this area too, but unfortunately, remove_proc_entry may be called with spinlocks held. The BKL may schedule, so this was not a solution. The final solution was to add a new global spin lock to protect this list, called proc_subdir_lock. This lock now protects the list in remove_proc_entry, and I also went around looking for other areas that this list is modified and added this protection there too. Care must be taken since these locations call several functions that may also schedule. Since I don't see any location that these functions that modify the subdirectory list are called by interrupts, the irqsave/restore versions of the spin lock was _not_ used. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs/proc/generic.c')
-rw-r--r--fs/proc/generic.c32
1 files changed, 29 insertions, 3 deletions
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 20e5c4509a4..47b7a20d45e 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -19,6 +19,7 @@
#include <linux/idr.h>
#include <linux/namei.h>
#include <linux/bitops.h>
+#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include "internal.h"
@@ -29,6 +30,8 @@ static ssize_t proc_file_write(struct file *file, const char __user *buffer,
size_t count, loff_t *ppos);
static loff_t proc_file_lseek(struct file *, loff_t, int);
+DEFINE_SPINLOCK(proc_subdir_lock);
+
int proc_match(int len, const char *name, struct proc_dir_entry *de)
{
if (de->namelen != len)
@@ -277,7 +280,9 @@ static int xlate_proc_name(const char *name,
const char *cp = name, *next;
struct proc_dir_entry *de;
int len;
+ int rtn = 0;
+ spin_lock(&proc_subdir_lock);
de = &proc_root;
while (1) {
next = strchr(cp, '/');
@@ -289,13 +294,17 @@ static int xlate_proc_name(const char *name,
if (proc_match(len, cp, de))
break;
}
- if (!de)
- return -ENOENT;
+ if (!de) {
+ rtn = -ENOENT;
+ goto out;
+ }
cp += len + 1;
}
*residual = cp;
*ret = de;
- return 0;
+out:
+ spin_unlock(&proc_subdir_lock);
+ return rtn;
}
static DEFINE_IDR(proc_inum_idr);
@@ -380,6 +389,7 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
int error = -ENOENT;
lock_kernel();
+ spin_lock(&proc_subdir_lock);
de = PDE(dir);
if (de) {
for (de = de->subdir; de ; de = de->next) {
@@ -388,12 +398,15 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
unsigned int ino = de->low_ino;
+ spin_unlock(&proc_subdir_lock);
error = -EINVAL;
inode = proc_get_inode(dir->i_sb, ino, de);
+ spin_lock(&proc_subdir_lock);
break;
}
}
}
+ spin_unlock(&proc_subdir_lock);
unlock_kernel();
if (inode) {
@@ -447,11 +460,13 @@ int proc_readdir(struct file * filp,
filp->f_pos++;
/* fall through */
default:
+ spin_lock(&proc_subdir_lock);
de = de->subdir;
i -= 2;
for (;;) {
if (!de) {
ret = 1;
+ spin_unlock(&proc_subdir_lock);
goto out;
}
if (!i)
@@ -461,12 +476,16 @@ int proc_readdir(struct file * filp,
}
do {
+ /* filldir passes info to user space */
+ spin_unlock(&proc_subdir_lock);
if (filldir(dirent, de->name, de->namelen, filp->f_pos,
de->low_ino, de->mode >> 12) < 0)
goto out;
+ spin_lock(&proc_subdir_lock);
filp->f_pos++;
de = de->next;
} while (de);
+ spin_unlock(&proc_subdir_lock);
}
ret = 1;
out: unlock_kernel();
@@ -500,9 +519,13 @@ static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp
if (i == 0)
return -EAGAIN;
dp->low_ino = i;
+
+ spin_lock(&proc_subdir_lock);
dp->next = dir->subdir;
dp->parent = dir;
dir->subdir = dp;
+ spin_unlock(&proc_subdir_lock);
+
if (S_ISDIR(dp->mode)) {
if (dp->proc_iops == NULL) {
dp->proc_fops = &proc_dir_operations;
@@ -694,6 +717,8 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
if (!parent && xlate_proc_name(name, &parent, &fn) != 0)
goto out;
len = strlen(fn);
+
+ spin_lock(&proc_subdir_lock);
for (p = &parent->subdir; *p; p=&(*p)->next ) {
if (!proc_match(len, fn, *p))
continue;
@@ -714,6 +739,7 @@ void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
}
break;
}
+ spin_unlock(&proc_subdir_lock);
out:
return;
}