From: Valerie Aurora <vaurora@xxxxxxxxxx>
---
fs/namei.c | 23 ++++++++++++++++++++---
1 files changed, 20 insertions(+), 3 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index fafd352..2b4780a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3519,10 +3519,12 @@ SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
{
struct dentry *new_dentry;
struct nameidata nd;
+ struct nameidata old_nd;
struct path old_path;
int how = 0;
int error;
char *to;
+ char *from;
if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
return -EINVAL;
@@ -3540,7 +3542,8 @@ SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
if (flags & AT_SYMLINK_FOLLOW)
how |= LOOKUP_FOLLOW;
- error = user_path_at(olddfd, oldname, how, &old_path);
+ error = user_path_nd(olddfd, oldname, how,
+ &old_nd, &old_path, &from);
if (error)
return error;
@@ -3548,8 +3551,20 @@ SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
if (error)
goto out;
error = -EXDEV;
- if (old_path.mnt != nd.path.mnt)
- goto out_release;
+ if (old_path.mnt != nd.path.mnt) {
+ if (IS_DIR_UNIONED(old_nd.path.dentry) &&
+ (old_nd.path.mnt == nd.path.mnt)) {
+ error = mnt_want_write(old_nd.path.mnt);
+ if (error)
+ goto out_release;
+ error = union_copyup(&old_nd, &old_path);
+ mnt_drop_write(old_nd.path.mnt);
+ if (error)
+ goto out_release;
+ } else {
+ goto out_release;
+ }
+ }
new_dentry = lookup_create(&nd, 0);
error = PTR_ERR(new_dentry);
if (IS_ERR(new_dentry))
@@ -3572,6 +3587,8 @@ out_release:
putname(to);
out:
path_put(&old_path);
+ path_put(&old_nd.path);
+ putname(from);
return error;
}
--
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