[PATCH] 9p: fix segfault caused by race condition in meta-data operations
Running dbench multithreaded exposed a race condition where fid structures
were removed while in use. This patch adds semaphores to meta-data operations
to protect the fid structure. Some cleanup of error-case handling in the
inode operations is also included.
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/9p/fid.c b/fs/9p/fid.c
index 2750720..a9b6301 100644
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -25,6 +25,7 @@
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/idr.h>
+#include <asm/semaphore.h>
#include "debug.h"
#include "v9fs.h"
@@ -84,6 +85,7 @@
new->iounit = 0;
new->rdir_pos = 0;
new->rdir_fcall = NULL;
+ init_MUTEX(&new->lock);
INIT_LIST_HEAD(&new->list);
return new;
@@ -102,11 +104,11 @@
}
/**
- * v9fs_fid_lookup - retrieve the right fid from a particular dentry
+ * v9fs_fid_lookup - return a locked fid from a dentry
* @dentry: dentry to look for fid in
- * @type: intent of lookup (operation or traversal)
*
- * find a fid in the dentry
+ * find a fid in the dentry, obtain its semaphore and return a reference to it.
+ * code calling lookup is responsible for releasing lock
*
* TODO: only match fids that have the same uid as current user
*
@@ -124,7 +126,68 @@
if (!return_fid) {
dprintk(DEBUG_ERROR, "Couldn't find a fid in dentry\n");
+ return_fid = ERR_PTR(-EBADF);
}
+ if(down_interruptible(&return_fid->lock))
+ return ERR_PTR(-EINTR);
+
return return_fid;
}
+
+/**
+ * v9fs_fid_clone - lookup the fid for a dentry, clone a private copy and release it
+ * @dentry: dentry to look for fid in
+ *
+ * find a fid in the dentry and then clone to a new private fid
+ *
+ * TODO: only match fids that have the same uid as current user
+ *
+ */
+
+struct v9fs_fid *v9fs_fid_clone(struct dentry *dentry)
+{
+ struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dentry->d_inode);
+ struct v9fs_fid *base_fid, *new_fid = ERR_PTR(-EBADF);
+ struct v9fs_fcall *fcall = NULL;
+ int fid, err;
+
+ base_fid = v9fs_fid_lookup(dentry);
+
+ if(IS_ERR(base_fid))
+ return base_fid;
+
+ if(base_fid) { /* clone fid */
+ fid = v9fs_get_idpool(&v9ses->fidpool);
+ if (fid < 0) {
+ eprintk(KERN_WARNING, "newfid fails!\n");
+ new_fid = ERR_PTR(-ENOSPC);
+ goto Release_Fid;
+ }
+
+ err = v9fs_t_walk(v9ses, base_fid->fid, fid, NULL, &fcall);
+ if (err < 0) {
+ dprintk(DEBUG_ERROR, "clone walk didn't work\n");
+ v9fs_put_idpool(fid, &v9ses->fidpool);
+ new_fid = ERR_PTR(err);
+ goto Free_Fcall;
+ }
+ new_fid = v9fs_fid_create(v9ses, fid);
+ if (new_fid == NULL) {
+ dprintk(DEBUG_ERROR, "out of memory\n");
+ new_fid = ERR_PTR(-ENOMEM);
+ }
+Free_Fcall:
+ kfree(fcall);
+ }
+
+Release_Fid:
+ up(&base_fid->lock);
+ return new_fid;
+}
+
+void v9fs_fid_clunk(struct v9fs_session_info *v9ses, struct v9fs_fid *fid)
+{
+ v9fs_t_clunk(v9ses, fid->fid);
+ v9fs_fid_destroy(fid);
+}
diff --git a/fs/9p/fid.h b/fs/9p/fid.h
index aa974d6..48fc170 100644
--- a/fs/9p/fid.h
+++ b/fs/9p/fid.h
@@ -30,6 +30,8 @@
struct list_head list; /* list of fids associated with a dentry */
struct list_head active; /* XXX - debug */
+ struct semaphore lock;
+
u32 fid;
unsigned char fidopen; /* set when fid is opened */
unsigned char fidclunked; /* set when fid has already been clunked */
@@ -55,3 +57,6 @@
void v9fs_fid_destroy(struct v9fs_fid *fid);
struct v9fs_fid *v9fs_fid_create(struct v9fs_session_info *, int fid);
int v9fs_fid_insert(struct v9fs_fid *fid, struct dentry *dentry);
+struct v9fs_fid *v9fs_fid_clone(struct dentry *dentry);
+void v9fs_fid_clunk(struct v9fs_session_info *v9ses, struct v9fs_fid *fid);
+
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index e86a071..9f17b0c 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -55,53 +55,22 @@
struct v9fs_fid *vfid;
struct v9fs_fcall *fcall = NULL;
int omode;
- int fid = V9FS_NOFID;
int err;
dprintk(DEBUG_VFS, "inode: %p file: %p \n", inode, file);
- vfid = v9fs_fid_lookup(file->f_path.dentry);
- if (!vfid) {
- dprintk(DEBUG_ERROR, "Couldn't resolve fid from dentry\n");
- return -EBADF;
- }
+ vfid = v9fs_fid_clone(file->f_path.dentry);
+ if (IS_ERR(vfid))
+ return PTR_ERR(vfid);
- fid = v9fs_get_idpool(&v9ses->fidpool);
- if (fid < 0) {
- eprintk(KERN_WARNING, "newfid fails!\n");
- return -ENOSPC;
- }
-
- err = v9fs_t_walk(v9ses, vfid->fid, fid, NULL, &fcall);
- if (err < 0) {
- dprintk(DEBUG_ERROR, "rewalk didn't work\n");
- if (fcall && fcall->id == RWALK)
- goto clunk_fid;
- else {
- v9fs_put_idpool(fid, &v9ses->fidpool);
- goto free_fcall;
- }
- }
- kfree(fcall);
-
- /* TODO: do special things for O_EXCL, O_NOFOLLOW, O_SYNC */
- /* translate open mode appropriately */
omode = v9fs_uflags2omode(file->f_flags);
- err = v9fs_t_open(v9ses, fid, omode, &fcall);
+ err = v9fs_t_open(v9ses, vfid->fid, omode, &fcall);
if (err < 0) {
PRINT_FCALL_ERROR("open failed", fcall);
- goto clunk_fid;
- }
-
- vfid = kmalloc(sizeof(struct v9fs_fid), GFP_KERNEL);
- if (vfid == NULL) {
- dprintk(DEBUG_ERROR, "out of memory\n");
- err = -ENOMEM;
- goto clunk_fid;
+ goto Clunk_Fid;
}
file->private_data = vfid;
- vfid->fid = fid;
vfid->fidopen = 1;
vfid->fidclunked = 0;
vfid->iounit = fcall->params.ropen.iounit;
@@ -112,10 +81,8 @@
return 0;
-clunk_fid:
- v9fs_t_clunk(v9ses, fid);
-
-free_fcall:
+Clunk_Fid:
+ v9fs_fid_clunk(v9ses, vfid);
kfree(fcall);
return err;
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 05d30e8..9109ba1 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -416,12 +416,8 @@
sb = file_inode->i_sb;
v9ses = v9fs_inode2v9ses(file_inode);
v9fid = v9fs_fid_lookup(file);
-
- if (!v9fid) {
- dprintk(DEBUG_ERROR,
- "no v9fs_fid\n");
- return -EBADF;
- }
+ if(IS_ERR(v9fid))
+ return PTR_ERR(v9fid);
fid = v9fid->fid;
if (fid < 0) {
@@ -433,11 +429,13 @@
result = v9fs_t_remove(v9ses, fid, &fcall);
if (result < 0) {
PRINT_FCALL_ERROR("remove fails", fcall);
+ goto Error;
}
v9fs_put_idpool(fid, &v9ses->fidpool);
v9fs_fid_destroy(v9fid);
+Error:
kfree(fcall);
return result;
}
@@ -473,9 +471,13 @@
inode = NULL;
vfid = NULL;
v9ses = v9fs_inode2v9ses(dir);
- dfid = v9fs_fid_lookup(dentry->d_parent);
- perm = unixmode2p9mode(v9ses, mode);
+ dfid = v9fs_fid_clone(dentry->d_parent);
+ if(IS_ERR(dfid)) {
+ err = PTR_ERR(dfid);
+ goto error;
+ }
+ perm = unixmode2p9mode(v9ses, mode);
if (nd && nd->flags & LOOKUP_OPEN)
flags = nd->intent.open.flags - 1;
else
@@ -485,9 +487,10 @@
perm, v9fs_uflags2omode(flags), NULL, &fid, &qid, &iounit);
if (err)
- goto error;
+ goto clunk_dfid;
vfid = v9fs_clone_walk(v9ses, dfid->fid, dentry);
+ v9fs_fid_clunk(v9ses, dfid);
if (IS_ERR(vfid)) {
err = PTR_ERR(vfid);
vfid = NULL;
@@ -525,6 +528,9 @@
return 0;
+clunk_dfid:
+ v9fs_fid_clunk(v9ses, dfid);
+
error:
if (vfid)
v9fs_fid_destroy(vfid);
@@ -551,7 +557,12 @@
inode = NULL;
vfid = NULL;
v9ses = v9fs_inode2v9ses(dir);
- dfid = v9fs_fid_lookup(dentry->d_parent);
+ dfid = v9fs_fid_clone(dentry->d_parent);
+ if(IS_ERR(dfid)) {
+ err = PTR_ERR(dfid);
+ goto error;
+ }
+
perm = unixmode2p9mode(v9ses, mode | S_IFDIR);
err = v9fs_create(v9ses, dfid->fid, (char *) dentry->d_name.name,
@@ -559,37 +570,36 @@
if (err) {
dprintk(DEBUG_ERROR, "create error %d\n", err);
- goto error;
- }
-
- err = v9fs_t_clunk(v9ses, fid);
- if (err) {
- dprintk(DEBUG_ERROR, "clunk error %d\n", err);
- goto error;
+ goto clean_up_dfid;
}
vfid = v9fs_clone_walk(v9ses, dfid->fid, dentry);
if (IS_ERR(vfid)) {
err = PTR_ERR(vfid);
vfid = NULL;
- goto error;
+ goto clean_up_dfid;
}
+ v9fs_fid_clunk(v9ses, dfid);
inode = v9fs_inode_from_fid(v9ses, vfid->fid, dir->i_sb);
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
inode = NULL;
- goto error;
+ goto clean_up_fids;
}
dentry->d_op = &v9fs_dentry_operations;
d_instantiate(dentry, inode);
return 0;
-error:
+clean_up_fids:
if (vfid)
v9fs_fid_destroy(vfid);
+clean_up_dfid:
+ v9fs_fid_clunk(v9ses, dfid);
+
+error:
return err;
}
@@ -622,28 +632,23 @@
dentry->d_op = &v9fs_dentry_operations;
dirfid = v9fs_fid_lookup(dentry->d_parent);
- if (!dirfid) {
- dprintk(DEBUG_ERROR, "no dirfid\n");
- return ERR_PTR(-EINVAL);
- }
+ if(IS_ERR(dirfid))
+ return ERR_PTR(PTR_ERR(dirfid));
dirfidnum = dirfid->fid;
- if (dirfidnum < 0) {
- dprintk(DEBUG_ERROR, "no dirfid for inode %p, #%lu\n",
- dir, dir->i_ino);
- return ERR_PTR(-EBADF);
- }
-
newfid = v9fs_get_idpool(&v9ses->fidpool);
if (newfid < 0) {
eprintk(KERN_WARNING, "newfid fails!\n");
- return ERR_PTR(-ENOSPC);
+ result = -ENOSPC;
+ goto Release_Dirfid;
}
result = v9fs_t_walk(v9ses, dirfidnum, newfid,
(char *)dentry->d_name.name, &fcall);
+ up(&dirfid->lock);
+
if (result < 0) {
if (fcall && fcall->id == RWALK)
v9fs_t_clunk(v9ses, newfid);
@@ -701,8 +706,12 @@
return NULL;
- FreeFcall:
+Release_Dirfid:
+ up(&dirfid->lock);
+
+FreeFcall:
kfree(fcall);
+
return ERR_PTR(result);
}
@@ -746,10 +755,8 @@
struct inode *old_inode = old_dentry->d_inode;
struct v9fs_session_info *v9ses = v9fs_inode2v9ses(old_inode);
struct v9fs_fid *oldfid = v9fs_fid_lookup(old_dentry);
- struct v9fs_fid *olddirfid =
- v9fs_fid_lookup(old_dentry->d_parent);
- struct v9fs_fid *newdirfid =
- v9fs_fid_lookup(new_dentry->d_parent);
+ struct v9fs_fid *olddirfid;
+ struct v9fs_fid *newdirfid;
struct v9fs_wstat wstat;
struct v9fs_fcall *fcall = NULL;
int fid = -1;
@@ -759,16 +766,26 @@
dprintk(DEBUG_VFS, "\n");
- if ((!oldfid) || (!olddirfid) || (!newdirfid)) {
- dprintk(DEBUG_ERROR, "problem with arguments\n");
- return -EBADF;
+ if(IS_ERR(oldfid))
+ return PTR_ERR(oldfid);
+
+ olddirfid = v9fs_fid_clone(old_dentry->d_parent);
+ if(IS_ERR(olddirfid)) {
+ retval = PTR_ERR(olddirfid);
+ goto Release_lock;
+ }
+
+ newdirfid = v9fs_fid_clone(new_dentry->d_parent);
+ if(IS_ERR(newdirfid)) {
+ retval = PTR_ERR(newdirfid);
+ goto Clunk_olddir;
}
/* 9P can only handle file rename in the same directory */
if (memcmp(&olddirfid->qid, &newdirfid->qid, sizeof(newdirfid->qid))) {
dprintk(DEBUG_ERROR, "old dir and new dir are different\n");
retval = -EXDEV;
- goto FreeFcallnBail;
+ goto Clunk_newdir;
}
fid = oldfid->fid;
@@ -779,7 +796,7 @@
dprintk(DEBUG_ERROR, "no fid for old file #%lu\n",
old_inode->i_ino);
retval = -EBADF;
- goto FreeFcallnBail;
+ goto Clunk_newdir;
}
v9fs_blank_wstat(&wstat);
@@ -788,11 +805,20 @@
retval = v9fs_t_wstat(v9ses, fid, &wstat, &fcall);
- FreeFcallnBail:
if (retval < 0)
PRINT_FCALL_ERROR("wstat error", fcall);
kfree(fcall);
+
+Clunk_newdir:
+ v9fs_fid_clunk(v9ses, newdirfid);
+
+Clunk_olddir:
+ v9fs_fid_clunk(v9ses, olddirfid);
+
+Release_lock:
+ up(&oldfid->lock);
+
return retval;
}
@@ -810,15 +836,12 @@
{
struct v9fs_fcall *fcall = NULL;
struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dentry->d_inode);
- struct v9fs_fid *fid = v9fs_fid_lookup(dentry);
+ struct v9fs_fid *fid = v9fs_fid_clone(dentry);
int err = -EPERM;
dprintk(DEBUG_VFS, "dentry: %p\n", dentry);
- if (!fid) {
- dprintk(DEBUG_ERROR,
- "couldn't find fid associated with dentry\n");
- return -EBADF;
- }
+ if(IS_ERR(fid))
+ return PTR_ERR(fid);
err = v9fs_t_stat(v9ses, fid->fid, &fcall);
@@ -831,6 +854,7 @@
}
kfree(fcall);
+ v9fs_fid_clunk(v9ses, fid);
return err;
}
@@ -844,18 +868,14 @@
static int v9fs_vfs_setattr(struct dentry *dentry, struct iattr *iattr)
{
struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dentry->d_inode);
- struct v9fs_fid *fid = v9fs_fid_lookup(dentry);
+ struct v9fs_fid *fid = v9fs_fid_clone(dentry);
struct v9fs_fcall *fcall = NULL;
struct v9fs_wstat wstat;
int res = -EPERM;
dprintk(DEBUG_VFS, "\n");
-
- if (!fid) {
- dprintk(DEBUG_ERROR,
- "Couldn't find fid associated with dentry\n");
- return -EBADF;
- }
+ if(IS_ERR(fid))
+ return PTR_ERR(fid);
v9fs_blank_wstat(&wstat);
if (iattr->ia_valid & ATTR_MODE)
@@ -887,6 +907,7 @@
if (res >= 0)
res = inode_setattr(dentry->d_inode, iattr);
+ v9fs_fid_clunk(v9ses, fid);
return res;
}
@@ -987,18 +1008,15 @@
struct v9fs_fcall *fcall = NULL;
struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dentry->d_inode);
- struct v9fs_fid *fid = v9fs_fid_lookup(dentry);
+ struct v9fs_fid *fid = v9fs_fid_clone(dentry);
- if (!fid) {
- dprintk(DEBUG_ERROR, "could not resolve fid from dentry\n");
- retval = -EBADF;
- goto FreeFcall;
- }
+ if(IS_ERR(fid))
+ return PTR_ERR(fid);
if (!v9ses->extended) {
retval = -EBADF;
dprintk(DEBUG_ERROR, "not extended\n");
- goto FreeFcall;
+ goto ClunkFid;
}
dprintk(DEBUG_VFS, " %s\n", dentry->d_name.name);
@@ -1009,8 +1027,10 @@
goto FreeFcall;
}
- if (!fcall)
- return -EIO;
+ if (!fcall) {
+ retval = -EIO;
+ goto ClunkFid;
+ }
if (!(fcall->params.rstat.stat.mode & V9FS_DMSYMLINK)) {
retval = -EINVAL;
@@ -1028,9 +1048,12 @@
fcall->params.rstat.stat.extension.str, buffer);
retval = buflen;
- FreeFcall:
+FreeFcall:
kfree(fcall);
+ClunkFid:
+ v9fs_fid_clunk(v9ses, fid);
+
return retval;
}
@@ -1123,52 +1146,58 @@
int err;
u32 fid, perm;
struct v9fs_session_info *v9ses;
- struct v9fs_fid *dfid, *vfid;
- struct inode *inode;
+ struct v9fs_fid *dfid, *vfid = NULL;
+ struct inode *inode = NULL;
- inode = NULL;
- vfid = NULL;
v9ses = v9fs_inode2v9ses(dir);
- dfid = v9fs_fid_lookup(dentry->d_parent);
- perm = unixmode2p9mode(v9ses, mode);
-
if (!v9ses->extended) {
dprintk(DEBUG_ERROR, "not extended\n");
return -EPERM;
}
+ dfid = v9fs_fid_clone(dentry->d_parent);
+ if(IS_ERR(dfid)) {
+ err = PTR_ERR(dfid);
+ goto error;
+ }
+
+ perm = unixmode2p9mode(v9ses, mode);
+
err = v9fs_create(v9ses, dfid->fid, (char *) dentry->d_name.name,
perm, V9FS_OREAD, (char *) extension, &fid, NULL, NULL);
if (err)
- goto error;
+ goto clunk_dfid;
err = v9fs_t_clunk(v9ses, fid);
if (err)
- goto error;
+ goto clunk_dfid;
vfid = v9fs_clone_walk(v9ses, dfid->fid, dentry);
if (IS_ERR(vfid)) {
err = PTR_ERR(vfid);
vfid = NULL;
- goto error;
+ goto clunk_dfid;
}
inode = v9fs_inode_from_fid(v9ses, vfid->fid, dir->i_sb);
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
inode = NULL;
- goto error;
+ goto free_vfid;
}
dentry->d_op = &v9fs_dentry_operations;
d_instantiate(dentry, inode);
return 0;
-error:
- if (vfid)
- v9fs_fid_destroy(vfid);
+free_vfid:
+ v9fs_fid_destroy(vfid);
+clunk_dfid:
+ v9fs_fid_clunk(v9ses, dfid);
+
+error:
return err;
}
@@ -1209,26 +1238,29 @@
struct dentry *dentry)
{
int retval;
+ struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dir);
struct v9fs_fid *oldfid;
char *name;
dprintk(DEBUG_VFS, " %lu,%s,%s\n", dir->i_ino, dentry->d_name.name,
old_dentry->d_name.name);
- oldfid = v9fs_fid_lookup(old_dentry);
- if (!oldfid) {
- dprintk(DEBUG_ERROR, "can't find oldfid\n");
- return -EPERM;
- }
+ oldfid = v9fs_fid_clone(old_dentry);
+ if(IS_ERR(oldfid))
+ return PTR_ERR(oldfid);
name = __getname();
- if (unlikely(!name))
- return -ENOMEM;
+ if (unlikely(!name)) {
+ retval = -ENOMEM;
+ goto clunk_fid;
+ }
sprintf(name, "%d\n", oldfid->fid);
retval = v9fs_vfs_mkspecial(dir, dentry, V9FS_DMLINK, name);
__putname(name);
+clunk_fid:
+ v9fs_fid_clunk(v9ses, oldfid);
return retval;
}