From e163fdb3f7f8c62dccf194f3f37a7bcb3c333aa8 Mon Sep 17 00:00:00 2001
From: Kees Cook <keescook@chromium.org>
Date: Wed, 8 Jan 2020 10:06:54 -0800
Subject: [PATCH] pstore/ram: Regularize prz label allocation lifetime
Git-commit: e163fdb3f7f8c62dccf194f3f37a7bcb3c333aa8
Patch-mainline: v5.5-rc6
References: git-fixes

In my attempt to fix a memory leak, I introduced a double-free in the
pstore error path. Instead of trying to manage the allocation lifetime
between persistent_ram_new() and its callers, adjust the logic so
persistent_ram_new() always takes a kstrdup() copy, and leaves the
caller's allocation lifetime up to the caller. Therefore callers are
_always_ responsible for freeing their label. Before, it only needed
freeing when the prz itself failed to allocate, and not in any of the
other prz failure cases, which callers would have no visibility into,
which is the root design problem that lead to both the leak and now
double-free bugs.

Reported-by: Cengiz Can <cengiz@kernel.wtf>
Link: https://lore.kernel.org/lkml/d4ec59002ede4aaf9928c7f7526da87c@kernel.wtf
Fixes: 8df955a32a73 ("pstore/ram: Fix error-path memory leak in persistent_ram_new() callers")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 fs/pstore/ram.c      | 4 ++--
 fs/pstore/ram_core.c | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 487ee39b438a..013486b5125e 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -583,12 +583,12 @@ static int ramoops_init_przs(const char *name,
 		prz_ar[i] = persistent_ram_new(*paddr, zone_sz, sig,
 					       &cxt->ecc_info,
 					       cxt->memtype, flags, label);
+		kfree(label);
 		if (IS_ERR(prz_ar[i])) {
 			err = PTR_ERR(prz_ar[i]);
 			dev_err(dev, "failed to request %s mem region (0x%zx@0x%llx): %d\n",
 				name, record_size,
 				(unsigned long long)*paddr, err);
-			kfree(label);
 
 			while (i > 0) {
 				i--;
@@ -629,12 +629,12 @@ static int ramoops_init_prz(const char *name,
 	label = kasprintf(GFP_KERNEL, "ramoops:%s", name);
 	*prz = persistent_ram_new(*paddr, sz, sig, &cxt->ecc_info,
 				  cxt->memtype, PRZ_FLAG_ZAP_OLD, label);
+	kfree(label);
 	if (IS_ERR(*prz)) {
 		int err = PTR_ERR(*prz);
 
 		dev_err(dev, "failed to request %s mem region (0x%zx@0x%llx): %d\n",
 			name, sz, (unsigned long long)*paddr, err);
-		kfree(label);
 		return err;
 	}
 
diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index 8823f65888f0..1f4d8c06f9be 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -574,7 +574,7 @@ struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
 	/* Initialize general buffer state. */
 	raw_spin_lock_init(&prz->buffer_lock);
 	prz->flags = flags;
-	prz->label = label;
+	prz->label = kstrdup(label, GFP_KERNEL);
 
 	ret = persistent_ram_buffer_map(start, size, prz, memtype);
 	if (ret)
-- 
2.16.4