ext4 crypto: allocate the right amount of memory for the on-disk symlink

Previously we were taking the required padding when allocating space
for the on-disk symlink.  This caused a buffer overrun which could
trigger a krenel crash when running fsstress.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/crypto_fname.c b/fs/ext4/crypto_fname.c
index 23af41f..7dc4eb5 100644 (file)
--- a/fs/ext4/crypto_fname.c
+++ b/fs/ext4/crypto_fname.c
@@ -262,8 +262,20 @@ u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
        return ((size+blksize-1)/blksize)*blksize;
 }
 
-/**
- * ext4_fname_crypto_alloc_obuff() -
+unsigned ext4_fname_encrypted_size(struct inode *inode, u32 ilen)
+{
+       struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
+       int padding = 32;
+
+       if (ci)
+               padding = 4 << (ci->ci_flags & EXT4_POLICY_FLAGS_PAD_MASK);
+       if (ilen < EXT4_CRYPTO_BLOCK_SIZE)
+               ilen = EXT4_CRYPTO_BLOCK_SIZE;
+       return ext4_fname_crypto_round_up(ilen, padding);
+}
+
+/*
+ * ext4_fname_crypto_alloc_buffer() -
  *
  * Allocates an output buffer that is sufficient for the crypto operation
  * specified by the context and the direction.
@@ -271,15 +283,8 @@ u32 ext4_fname_crypto_round_up(u32 size, u32 blksize)
 int ext4_fname_crypto_alloc_buffer(struct inode *inode,
                                   u32 ilen, struct ext4_str *crypto_str)
 {
-       unsigned int olen;
-       int padding = 16;
-       struct ext4_crypt_info *ci = EXT4_I(inode)->i_crypt_info;
+       unsigned int olen = ext4_fname_encrypted_size(inode, ilen);
 
-       if (ci)
-               padding = 4 << (ci->ci_flags & EXT4_POLICY_FLAGS_PAD_MASK);
-       if (padding < EXT4_CRYPTO_BLOCK_SIZE)
-               padding = EXT4_CRYPTO_BLOCK_SIZE;
-       olen = ext4_fname_crypto_round_up(ilen, padding);
        crypto_str->len = olen;
        if (olen < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2)
                olen = EXT4_FNAME_CRYPTO_DIGEST_SIZE*2;

diff --cc fs/ext4/ext4.h
Simple merge

diff --cc fs/ext4/namei.c
Simple merge