In operations that involve pathwalks (lookups and atomic opens), ensure
that the operations are making forward progress. Save a copy of the
current nd.path.dentry when retrying on an estale and ensure that it's
changing on each pass through the loop. If it isn't, then we're stuck.
Just return -ENOENT in that case.
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/namei.c | 31 ++++++++++++++++++++++++++++---
1 file changed, 28 insertions(+), 3 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index c3582d4..f0916e6 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2021,12 +2021,21 @@ static int filename_lookup(int dfd, struct filename *name,
unsigned int flags, struct nameidata *nd)
{
unsigned int try = 0;
+ struct dentry *save = NULL;
int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd);
+
if (unlikely(retval == -ECHILD))
retval = path_lookupat(dfd, name->name, flags, nd);
- while (retry_estale(retval, try++))
+
+ while (retry_estale(retval, try++)) {
+ if (nd->path.dentry == save) {
+ retval = -ENOENT;
+ break;
+ }
+ save = nd->path.dentry;
retval = path_lookupat(dfd, name->name,
flags | LOOKUP_REVAL, nd);
+ }
if (likely(!retval))
audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
@@ -3014,12 +3023,20 @@ struct file *do_filp_open(int dfd, struct filename *pathname,
struct nameidata nd;
struct file *filp;
unsigned int try = 0;
+ struct dentry *save = NULL;
filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
if (unlikely(filp == ERR_PTR(-ECHILD)))
filp = path_openat(dfd, pathname, &nd, op, flags);
- while (retry_estale(PTR_ERR(filp), try++))
+
+ while (retry_estale(PTR_ERR(filp), try++)) {
+ if (nd.path.dentry == save) {
+ filp = ERR_PTR(-ENOENT);
+ break;
+ }
+ save = nd.path.dentry;
filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
+ }
return filp;
}
@@ -3030,6 +3047,7 @@ struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
struct file *file;
struct filename filename = { .name = name };
unsigned int try = 0;
+ struct dentry *save = NULL;
nd.root.mnt = mnt;
nd.root.dentry = dentry;
@@ -3042,8 +3060,15 @@ struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU);
if (unlikely(file == ERR_PTR(-ECHILD)))
file = path_openat(-1, &filename, &nd, op, flags);
- while (retry_estale(PTR_ERR(file), try++))
+
+ while (retry_estale(PTR_ERR(file), try++)) {
+ if (nd.path.dentry == save) {
+ file = ERR_PTR(-ENOENT);
+ break;
+ }
+ save = nd.path.dentry;
file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL);
+ }
return file;
}
--
1.7.11.7
--
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