fat: fix memory allocation failure handling of match_strdup()

PATCH In review [email protected] 1 participant 1 message Jul 21, 2018

Subsystems (2)

Stable branch VFAT/FAT/msdos filesystem

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2018-07-21 01:44 UTC #0 lore raw

PATCH 4/6 fat: fix memory allocation failure handling of match_strdup()

From: OGAWA Hirofumi <[email protected]>
Subject: fat: fix memory allocation failure handling of match_strdup()

In parse_options(), if match_strdup() failed, parse_options() leaves opts->iocharset in unexpected state (i.e. still pointing the freed string). And this can be the cause of double free.

To fix, this initialize opts->iocharset always when freeing.

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by OGAWA Hirofumi <[email protected]>

Reported-by [email protected]

Cc <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

---

 fs/fat/inode.c |   20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

fs/fat/inode.c renamed from fs/fat/inode.c~fat-fix-memory-allocation-failure-handling-of-match_strdup +13 -7

diff -puN fs/fat/inode.c~fat-fix-memory-allocation-failure-handling-of-match_strdup fs/fat/inode.c
@@ -707,13 +707,21 @@ static void fat_set_state(struct super_b
 	brelse(bh);
 }
 
+static void fat_reset_iocharset(struct fat_mount_options *opts)
+{
+	if (opts->iocharset != fat_default_iocharset) {
+		/* Note: opts->iocharset can be NULL here */
+		kfree(opts->iocharset);
+		opts->iocharset = fat_default_iocharset;
+	}
+}
+
 static void delayed_free(struct rcu_head *p)
 {
 	struct msdos_sb_info *sbi = container_of(p, struct msdos_sb_info, rcu);
 	unload_nls(sbi->nls_disk);
 	unload_nls(sbi->nls_io);
-	if (sbi->options.iocharset != fat_default_iocharset)
-		kfree(sbi->options.iocharset);
+	fat_reset_iocharset(&sbi->options);
 	kfree(sbi);
 }

@@ -1132,7 +1140,7 @@ static int parse_options(struct super_bl
 	opts->fs_fmask = opts->fs_dmask = current_umask();
 	opts->allow_utime = -1;
 	opts->codepage = fat_default_codepage;
-	opts->iocharset = fat_default_iocharset;
+	fat_reset_iocharset(opts);
 	if (is_vfat) {
 		opts->shortname = VFAT_SFN_DISPLAY_WINNT|VFAT_SFN_CREATE_WIN95;
 		opts->rodir = 0;

@@ -1289,8 +1297,7 @@ static int parse_options(struct super_bl
 
 		/* vfat specific */
 		case Opt_charset:
-			if (opts->iocharset != fat_default_iocharset)
-				kfree(opts->iocharset);
+			fat_reset_iocharset(opts);
 			iocharset = match_strdup(&args[0]);
 			if (!iocharset)
 				return -ENOMEM;

@@ -1881,8 +1888,7 @@ out_fail:
 		iput(fat_inode);
 	unload_nls(sbi->nls_io);
 	unload_nls(sbi->nls_disk);
-	if (sbi->options.iocharset != fat_default_iocharset)
-		kfree(sbi->options.iocharset);
+	fat_reset_iocharset(&sbi->options);
 	sb->s_fs_info = NULL;
 	kfree(sbi);
 	return error;