[PATCH v3 4/9] cachefiles: propagate errors from vfs_getxattr() to avoid infinite loop

[libaokun]

From: Baokun Li <libaok...@huawei.com>

In cachefiles_check_volume_xattr(), the error returned by vfs_getxattr()
is not passed to ret, so it ends up returning -ESTALE, which leads to an
endless loop as follows:

cachefiles_acquire_volume
retry:
  ret = cachefiles_check_volume_xattr
    ret = -ESTALE
    xlen = vfs_getxattr // return -EIO
    // The ret is not updated when xlen < 0, so -ESTALE is returned.
    return ret
  // Supposed to jump out of the loop at this judgement.
  if (ret != -ESTALE)
      goto error_dir;
  cachefiles_bury_object
    //  EIO causes rename failure
  goto retry;

Hence propagate the error returned by vfs_getxattr() to avoid the above
issue. Do the same in cachefiles_check_auxdata().

Fixes: 32e150037dce ("fscache, cachefiles: Store the volume coherency data")
Fixes: 72b957856b0c ("cachefiles: Implement metadata/coherency data storage in 
xattrs")
Signed-off-by: Baokun Li <libaok...@huawei.com>
---
 fs/cachefiles/xattr.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c
index bcb6173943ee..4dd8a993c60a 100644
--- a/fs/cachefiles/xattr.c
+++ b/fs/cachefiles/xattr.c
@@ -110,9 +110,11 @@ int cachefiles_check_auxdata(struct cachefiles_object 
*object, struct file *file
        if (xlen == 0)
                xlen = vfs_getxattr(&nop_mnt_idmap, dentry, 
cachefiles_xattr_cache, buf, tlen);
        if (xlen != tlen) {
-               if (xlen < 0)
+               if (xlen < 0) {
+                       ret = xlen;
                        trace_cachefiles_vfs_error(object, file_inode(file), 
xlen,
                                                   
cachefiles_trace_getxattr_error);
+               }
                if (xlen == -EIO)
                        cachefiles_io_error_obj(
                                object,
@@ -252,6 +254,7 @@ int cachefiles_check_volume_xattr(struct cachefiles_volume 
*volume)
                xlen = vfs_getxattr(&nop_mnt_idmap, dentry, 
cachefiles_xattr_cache, buf, len);
        if (xlen != len) {
                if (xlen < 0) {
+                       ret = xlen;
                        trace_cachefiles_vfs_error(NULL, d_inode(dentry), xlen,
                                                   
cachefiles_trace_getxattr_error);
                        if (xlen == -EIO)
-- 
2.39.2