FAILED: patch "[PATCH] cachefiles: fix memory leak in cachefiles_add_cache()" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x e21a2f17566cbd64926fb8f16323972f7a064444
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024022639-selection-angrily-d6ff@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

e21a2f17566c ("cachefiles: fix memory leak in cachefiles_add_cache()") d1065b0a6fd9 ("cachefiles: Implement cache registration and withdrawal") 32759f7d7af5 ("cachefiles: Implement a function to get/create a directory in the cache") 1bd9c4e4f049 ("vfs, cachefiles: Mark a backing file in use with an inode flag") 80f94f29f677 ("cachefiles: Provide a function to check how much space there is") 8667d434b2a9 ("cachefiles: Register a miscdev and parse commands over it") 254947d47945 ("cachefiles: Add security derivation")
1493bf74bcf2 ("cachefiles: Add cache error reporting macro")
ecf5a6ce15f9 ("cachefiles: Add a couple of tracepoints for logging errors") a70f6526267e ("cachefiles: Add some error injection support")
8390fbc46570 ("cachefiles: Define structs")
77443f6171f3 ("cachefiles: Introduce rewritten driver")
850cba069c26 ("cachefiles: Delete the cachefiles driver pending rewrite") b6773cdb0e9f ("Merge tag 'for-5.16/ki_complete-2021-10-29' of git://git.kernel.dk/linux-block")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e21a2f17566cbd64926fb8f16323972f7a064444 Mon Sep 17 00:00:00 2001
From: Baokun Li <[email protected]>
Date: Sat, 17 Feb 2024 16:14:31 +0800
Subject: [PATCH] cachefiles: fix memory leak in cachefiles_add_cache()

The following memory leak was reported after unbinding /dev/cachefiles:

==================================================================
unreferenced object 0xffff9b674176e3c0 (size 192):
comm "cachefilesd2", pid 680, jiffies 4294881224 hex dump (first 32 bytes):

    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc ea38a44b):
    [<ffffffff8eb8a1a5>] kmem_cache_alloc+0x2d5/0x370
    [<ffffffff8e917f86>] prepare_creds+0x26/0x2e0
    [<ffffffffc002eeef>] cachefiles_determine_cache_security+0x1f/0x120
    [<ffffffffc00243ec>] cachefiles_add_cache+0x13c/0x3a0
    [<ffffffffc0025216>] cachefiles_daemon_write+0x146/0x1c0
    [<ffffffff8ebc4a3b>] vfs_write+0xcb/0x520
    [<ffffffff8ebc5069>] ksys_write+0x69/0xf0
    [<ffffffff8f6d4662>] do_syscall_64+0x72/0x140
    [<ffffffff8f8000aa>] entry_SYSCALL_64_after_hwframe+0x6e/0x76
==================================================================

Put the reference count of cache_cred in cachefiles_daemon_unbind() to fix the problem. And also put cache_cred in cachefiles_add_cache() error branch to avoid memory leaks.

index 7077f72e6f47..f449f7340aad 100644
@@ -168,6 +168,8 @@ int cachefiles_add_cache(struct cachefiles_cache *cache)
 	dput(root);
 error_open_root:
 	cachefiles_end_secure(cache, saved_cred);
+	put_cred(cache->cache_cred);
+	cache->cache_cred = NULL;
 error_getsec:
 	fscache_relinquish_cache(cache_cookie);
 	cache->cache = NULL;

index 3f24905f4066..6465e2574230 100644
@@ -816,6 +816,7 @@ static void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
 	cachefiles_put_directory(cache->graveyard);
 	cachefiles_put_directory(cache->store);
 	mntput(cache->mnt);
+	put_cred(cache->cache_cred);
 
 	kfree(cache->rootdirname);
 	kfree(cache->secctx);