linux-ext4 - [PATCH 04/10] e2fsck: validate that fscrypt_symlink

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Date:   Fri,  2 Mar 2018 16:59:17 -0800
From:   Eric Biggers <ebiggers3@...il.com>
To:     linux-ext4@...r.kernel.org
Cc:     Eric Biggers <ebiggers@...gle.com>
Subject: [PATCH 04/10] e2fsck: validate that fscrypt_symlink_data.len is not too large

From: Eric Biggers <ebiggers@...gle.com>

Make e2fsck start validating that the ciphertext length stored in the
header of an encrypted symlink target, plus the header itself, is no
larger than a filesystem block.  Previously e2fsck only verified that
this size is not exactly equal to a filesystem block.  This was
sufficient for unencrypted symlinks, where the "actual length" is
computed using strnlen(), but not for encrypted symlinks; the kernel
also considers encrypted symlinks with too-large ciphertext length to be
invalid.

Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 e2fsck/pass1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
index b101df0a..723acf09 100644
--- a/e2fsck/pass1.c
+++ b/e2fsck/pass1.c
@@ -253,7 +253,7 @@ int e2fsck_pass1_check_symlink(ext2_filsys fs, ext2_ino_t ino,
 		} else {
 			len = strnlen(buf, fs->blocksize);
 		}
-		if (len == fs->blocksize)
+		if (len >= fs->blocksize)
 			return 0;
 	}
 	if (len != inode->i_size)
-- 
2.16.2.395.g2e18187dfd-goog