diff mbox series

[v4.19.y] ext4: validate the debug_want_extra_isize mount option at parse time

Message ID 20200201050601.148009-1-zsm@chromium.org
State New
Headers show
Series [v4.19.y] ext4: validate the debug_want_extra_isize mount option at parse time | expand

Commit Message

Zubin Mithra Feb. 1, 2020, 5:06 a.m. UTC 
From: Theodore Ts'o <tytso@mit.edu>

commit 9803387c55f7d2ce69aa64340c5fdc6b3027dbc8 upstream.

Instead of setting s_want_extra_size and then making sure that it is a
valid value afterwards, validate the field before we set it.  This
avoids races and other problems when remounting the file system.

Link: https://lore.kernel.org/r/20191215063020.GA11512@mit.edu
Cc: stable@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reported-and-tested-by: syzbot+4a39a025912b265cacef@syzkaller.appspotmail.com
Signed-off-by: Zubin Mithra <zsm@chromium.org>
---
Notes:
* Syzkaller triggered a UAF on 4.19 kernels with the following
stacktrace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0xc8/0x129 lib/dump_stack.c:113
 print_address_description+0x67/0x22a mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report+0x251/0x28f mm/kasan/report.c:396
 ext4_xattr_set_entry+0x45e/0x2222 fs/ext4/xattr.c:1604
 ext4_xattr_ibody_set+0x7d/0x226 fs/ext4/xattr.c:2240
 ext4_xattr_set_handle+0x553/0xa92 fs/ext4/xattr.c:2396
 ext4_xattr_set+0x16a/0x200 fs/ext4/xattr.c:2508
 __vfs_setxattr+0xfc/0x13d fs/xattr.c:149
 __vfs_setxattr_noperm+0xf5/0x19c fs/xattr.c:180
 vfs_setxattr+0x9c/0xca fs/xattr.c:223
 setxattr+0x20e/0x275 fs/xattr.c:450
 path_setxattr+0xca/0x144 fs/xattr.c:469
 __do_sys_lsetxattr fs/xattr.c:491 [inline]
 __se_sys_lsetxattr fs/xattr.c:487 [inline]
 __x64_sys_lsetxattr+0xd7/0xe1 fs/xattr.c:487
 do_syscall_64+0xfe/0x137 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

* This commit is present in linux-5.4.y. A backport for 4.14.y has been
sent separately.

* This patch resolves conflicts related to the following commits not
being present in linux-4.19.y:
	188d20bcd1eb ("vfs: Add file timestamp range support")
	4881c4971df0 ("ext4: Initialize timestamps limits")

* Tests run: Chrome OS tryjobs, Syzkaller reproducer

 fs/ext4/super.c | 127 +++++++++++++++++++++++++-----------------------
 1 file changed, 66 insertions(+), 61 deletions(-)
diff mbox series

Patch

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 1a8d57fe0b1a8..32d8bdf683bbf 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1842,6 +1842,13 @@  static int handle_mount_opt(struct super_block *sb, char *opt, int token,
 			arg = JBD2_DEFAULT_MAX_COMMIT_AGE;
 		sbi->s_commit_interval = HZ * arg;
 	} else if (token == Opt_debug_want_extra_isize) {
+		if ((arg & 1) ||
+		    (arg < 4) ||
+		    (arg > (sbi->s_inode_size - EXT4_GOOD_OLD_INODE_SIZE))) {
+			ext4_msg(sb, KERN_ERR,
+				 "Invalid want_extra_isize %d", arg);
+			return -1;
+		}
 		sbi->s_want_extra_isize = arg;
 	} else if (token == Opt_max_batch_time) {
 		sbi->s_max_batch_time = arg;
@@ -3513,40 +3520,6 @@  int ext4_calculate_overhead(struct super_block *sb)
 	return 0;
 }
 
-static void ext4_clamp_want_extra_isize(struct super_block *sb)
-{
-	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	struct ext4_super_block *es = sbi->s_es;
-	unsigned def_extra_isize = sizeof(struct ext4_inode) -
-						EXT4_GOOD_OLD_INODE_SIZE;
-
-	if (sbi->s_inode_size == EXT4_GOOD_OLD_INODE_SIZE) {
-		sbi->s_want_extra_isize = 0;
-		return;
-	}
-	if (sbi->s_want_extra_isize < 4) {
-		sbi->s_want_extra_isize = def_extra_isize;
-		if (ext4_has_feature_extra_isize(sb)) {
-			if (sbi->s_want_extra_isize <
-			    le16_to_cpu(es->s_want_extra_isize))
-				sbi->s_want_extra_isize =
-					le16_to_cpu(es->s_want_extra_isize);
-			if (sbi->s_want_extra_isize <
-			    le16_to_cpu(es->s_min_extra_isize))
-				sbi->s_want_extra_isize =
-					le16_to_cpu(es->s_min_extra_isize);
-		}
-	}
-	/* Check if enough inode space is available */
-	if ((sbi->s_want_extra_isize > sbi->s_inode_size) ||
-	    (EXT4_GOOD_OLD_INODE_SIZE + sbi->s_want_extra_isize >
-							sbi->s_inode_size)) {
-		sbi->s_want_extra_isize = def_extra_isize;
-		ext4_msg(sb, KERN_INFO,
-			 "required extra inode space not available");
-	}
-}
-
 static void ext4_set_resv_clusters(struct super_block *sb)
 {
 	ext4_fsblk_t resv_clusters;
@@ -3754,6 +3727,65 @@  static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	 */
 	sbi->s_li_wait_mult = EXT4_DEF_LI_WAIT_MULT;
 
+	if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV) {
+		sbi->s_inode_size = EXT4_GOOD_OLD_INODE_SIZE;
+		sbi->s_first_ino = EXT4_GOOD_OLD_FIRST_INO;
+	} else {
+		sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
+		sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
+		if (sbi->s_first_ino < EXT4_GOOD_OLD_FIRST_INO) {
+			ext4_msg(sb, KERN_ERR, "invalid first ino: %u",
+				 sbi->s_first_ino);
+			goto failed_mount;
+		}
+		if ((sbi->s_inode_size < EXT4_GOOD_OLD_INODE_SIZE) ||
+		    (!is_power_of_2(sbi->s_inode_size)) ||
+		    (sbi->s_inode_size > blocksize)) {
+			ext4_msg(sb, KERN_ERR,
+			       "unsupported inode size: %d",
+			       sbi->s_inode_size);
+			goto failed_mount;
+		}
+		/*
+		 * i_atime_extra is the last extra field available for
+		 * [acm]times in struct ext4_inode. Checking for that
+		 * field should suffice to ensure we have extra space
+		 * for all three.
+		 */
+		if (sbi->s_inode_size >= offsetof(struct ext4_inode, i_atime_extra) +
+			sizeof(((struct ext4_inode *)0)->i_atime_extra)) {
+			sb->s_time_gran = 1;
+		} else {
+			sb->s_time_gran = NSEC_PER_SEC;
+		}
+	}
+	if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE) {
+		sbi->s_want_extra_isize = sizeof(struct ext4_inode) -
+			EXT4_GOOD_OLD_INODE_SIZE;
+		if (ext4_has_feature_extra_isize(sb)) {
+			unsigned v, max = (sbi->s_inode_size -
+					   EXT4_GOOD_OLD_INODE_SIZE);
+
+			v = le16_to_cpu(es->s_want_extra_isize);
+			if (v > max) {
+				ext4_msg(sb, KERN_ERR,
+					 "bad s_want_extra_isize: %d", v);
+				goto failed_mount;
+			}
+			if (sbi->s_want_extra_isize < v)
+				sbi->s_want_extra_isize = v;
+
+			v = le16_to_cpu(es->s_min_extra_isize);
+			if (v > max) {
+				ext4_msg(sb, KERN_ERR,
+					 "bad s_min_extra_isize: %d", v);
+				goto failed_mount;
+			}
+			if (sbi->s_want_extra_isize < v)
+				sbi->s_want_extra_isize = v;
+		}
+	}
+
 	if (sbi->s_es->s_mount_opts[0]) {
 		char *s_mount_opts = kstrndup(sbi->s_es->s_mount_opts,
 					      sizeof(sbi->s_es->s_mount_opts),
@@ -3955,29 +3987,6 @@  static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 						      has_huge_files);
 	sb->s_maxbytes = ext4_max_size(sb->s_blocksize_bits, has_huge_files);
 
-	if (le32_to_cpu(es->s_rev_level) == EXT4_GOOD_OLD_REV) {
-		sbi->s_inode_size = EXT4_GOOD_OLD_INODE_SIZE;
-		sbi->s_first_ino = EXT4_GOOD_OLD_FIRST_INO;
-	} else {
-		sbi->s_inode_size = le16_to_cpu(es->s_inode_size);
-		sbi->s_first_ino = le32_to_cpu(es->s_first_ino);
-		if (sbi->s_first_ino < EXT4_GOOD_OLD_FIRST_INO) {
-			ext4_msg(sb, KERN_ERR, "invalid first ino: %u",
-				 sbi->s_first_ino);
-			goto failed_mount;
-		}
-		if ((sbi->s_inode_size < EXT4_GOOD_OLD_INODE_SIZE) ||
-		    (!is_power_of_2(sbi->s_inode_size)) ||
-		    (sbi->s_inode_size > blocksize)) {
-			ext4_msg(sb, KERN_ERR,
-			       "unsupported inode size: %d",
-			       sbi->s_inode_size);
-			goto failed_mount;
-		}
-		if (sbi->s_inode_size > EXT4_GOOD_OLD_INODE_SIZE)
-			sb->s_time_gran = 1 << (EXT4_EPOCH_BITS - 2);
-	}
-
 	sbi->s_desc_size = le16_to_cpu(es->s_desc_size);
 	if (ext4_has_feature_64bit(sb)) {
 		if (sbi->s_desc_size < EXT4_MIN_DESC_SIZE_64BIT ||
@@ -4421,8 +4430,6 @@  static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	} else if (ret)
 		goto failed_mount4a;
 
-	ext4_clamp_want_extra_isize(sb);
-
 	ext4_set_resv_clusters(sb);
 
 	err = ext4_setup_system_zone(sb);
@@ -5207,8 +5214,6 @@  static int ext4_remount(struct super_block *sb, int *flags, char *data)
 		goto restore_opts;
 	}
 
-	ext4_clamp_want_extra_isize(sb);
-
 	if ((old_opts.s_mount_opt & EXT4_MOUNT_JOURNAL_CHECKSUM) ^
 	    test_opt(sb, JOURNAL_CHECKSUM)) {
 		ext4_msg(sb, KERN_ERR, "changing journal_checksum "