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Subjectbuild_path_from_dentry_optional_prefix() may schedule from invalid context
Hello,

Looking at commit "cifs: create a helper to find a writeable handle
by path name":

->open_file_lock scope is atomic context, while build_path_from_dentry()
can schedule - kmalloc(GFP_KERNEL)

spin_lock(&tcon->open_file_lock);
list_for_each(tmp, &tcon->openFileList) {
cfile = list_entry(tmp, struct cifsFileInfo,
tlist);
full_path = build_path_from_dentry(cfile->dentry);
if (full_path == NULL) {
spin_unlock(&tcon->open_file_lock);
return -ENOMEM;
}
if (strcmp(full_path, name)) {
kfree(full_path);
continue;
}
kfree(full_path);

cinode = CIFS_I(d_inode(cfile->dentry));
spin_unlock(&tcon->open_file_lock);
return cifs_get_writable_file(cinode, 0, ret_file);
}

spin_unlock(&tcon->open_file_lock);

Additionally, kfree() can (and should) be done outside of
->open_file_lock scope.

-ss

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