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Date:   Wed, 17 Oct 2018 14:41:24 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Joel Fernandes <joel@joelfernandes.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Cc:     linux-kernel@vger.kernel.org
Subject: [PATCH] pstore: Refactor compression initialization
Message-ID: <20181017214124.GA8239@beast>
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Sender: linux-kernel-owner@vger.kernel.org
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With compression initialization now separated from pstore_register(),
there is no longer a good reason to do compression method selection
during fs init. Instead, merge everything together into the late init.
Additionally cleans up the reporting to be more clear.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
This patch goes on top of Joel's. I'll have both in linux-next shortly...
---
 fs/pstore/inode.c    |  2 --
 fs/pstore/internal.h |  3 --
 fs/pstore/platform.c | 65 ++++++++++++++++++++++++++++----------------
 3 files changed, 41 insertions(+), 29 deletions(-)

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 5fcb845b9fec..d814723fb27d 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -486,8 +486,6 @@ static int __init init_pstore_fs(void)
 {
 	int err;
 
-	pstore_choose_compression();
-
 	/* Create a convenient mount point for people to access pstore */
 	err = sysfs_create_mount_point(fs_kobj, "pstore");
 	if (err)
diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
index fb767e28aeb2..c029314478fa 100644
--- a/fs/pstore/internal.h
+++ b/fs/pstore/internal.h
@@ -37,7 +37,4 @@ extern bool	pstore_is_mounted(void);
 extern void	pstore_record_init(struct pstore_record *record,
 				   struct pstore_info *psi);
 
-/* Called during module_init() */
-extern void __init pstore_choose_compression(void);
-
 #endif
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index f09066db2d4d..e4737a5fa68c 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -274,36 +274,56 @@ static int pstore_decompress(void *in, void *out,
 
 static void allocate_buf_for_compression(void)
 {
+	struct crypto_comp *ctx;
+	int size;
+	char *buf;
+
+	/* Skip if not built-in or compression backend not selected yet. */
 	if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
 		return;
 
+	/* Skip if no pstore backend yet or compression init already done. */
+	if (!psinfo || tfm)
+		return;
+
 	if (!crypto_has_comp(zbackend->name, 0, 0)) {
-		pr_err("No %s compression\n", zbackend->name);
+		pr_err("Unknown compression: %s\n", zbackend->name);
 		return;
 	}
 
-	big_oops_buf_sz = zbackend->zbufsize(psinfo->bufsize);
-	if (big_oops_buf_sz <= 0)
+	size = zbackend->zbufsize(psinfo->bufsize);
+	if (size <= 0) {
+		pr_err("Invalid compression size for %s: %d\n",
+		       zbackend->name, size);
 		return;
+	}
 
-	big_oops_buf = kmalloc(big_oops_buf_sz, GFP_KERNEL);
-	if (!big_oops_buf) {
-		pr_err("allocate compression buffer error!\n");
+	buf = kmalloc(size, GFP_KERNEL);
+	if (!buf) {
+		pr_err("Failed %d byte compression buffer allocation for: %s\n",
+		       size, zbackend->name);
 		return;
 	}
 
-	tfm = crypto_alloc_comp(zbackend->name, 0, 0);
-	if (IS_ERR_OR_NULL(tfm)) {
-		kfree(big_oops_buf);
-		big_oops_buf = NULL;
-		pr_err("crypto_alloc_comp() failed!\n");
+	ctx = crypto_alloc_comp(zbackend->name, 0, 0);
+	if (IS_ERR_OR_NULL(ctx)) {
+		kfree(buf);
+		pr_err("crypto_alloc_comp('%s') failed: %ld\n", zbackend->name,
+		       PTR_ERR(ctx));
 		return;
 	}
+
+	/* A non-NULL big_oops_buf indicates compression is available. */
+	tfm = ctx;
+	big_oops_buf_sz = size;
+	big_oops_buf = buf;
+
+	pr_info("Using compression: %s\n", zbackend->name);
 }
 
 static void free_buf_for_compression(void)
 {
-	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && !IS_ERR_OR_NULL(tfm))
+	if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm)
 		crypto_free_comp(tfm);
 	kfree(big_oops_buf);
 	big_oops_buf = NULL;
@@ -764,31 +784,28 @@ static void pstore_timefunc(struct timer_list *unused)
 			  jiffies + msecs_to_jiffies(pstore_update_ms));
 }
 
-void __init pstore_choose_compression(void)
+static int __init pstore_compression_late_init(void)
 {
 	const struct pstore_zbackend *step;
 
 	if (!compress)
-		return;
+		return 0;
 
+	/* Locate desired compression method. */
 	for (step = zbackends; step->name; step++) {
 		if (!strcmp(compress, step->name)) {
 			zbackend = step;
-			pr_info("using %s compression\n", zbackend->name);
-			return;
+			break;
 		}
 	}
-}
 
-static int __init pstore_compression_late_init(void)
-{
 	/*
-	 * Check if any pstore backends registered earlier but did not allocate
-	 * for compression because crypto was not ready, if so then initialize
-	 * compression.
+	 * Check if any pstore backends registered earlier but did not
+	 * initialize compression because crypto was not ready. If so,
+	 * then initialize compression now.
 	 */
-	if (psinfo && !tfm)
-		allocate_buf_for_compression();
+	allocate_buf_for_compression();
+
 	return 0;
 }
 late_initcall(pstore_compression_late_init);
-- 
2.17.1


-- 
Kees Cook
Pixel Security