[PATCH] ext4: handle decryption error in __ext4_block_zero_page_range()

[PATCH] ext4: handle decryption error in __ext4_block_zero_page_range()

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

fscrypt_decrypt_pagecache_blocks() can fail, because it uses
skcipher_request_alloc(), which uses kmalloc(), which can fail; and also
because it calls crypto_skcipher_decrypt(), which can fail depending on
the driver that actually implements the crypto.

Therefore it's not appropriate to WARN on decryption error in
__ext4_block_zero_page_range().

Remove the WARN and just handle the error instead.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/ext4/inode.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 629a25d999f0..b8f8afd2e8b2 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3701,8 +3701,12 @@ static int __ext4_block_zero_page_range(handle_t *handle,
 		if (S_ISREG(inode->i_mode) && IS_ENCRYPTED(inode)) {
 			/* We expect the key to be set. */
 			BUG_ON(!fscrypt_has_encryption_key(inode));
-			WARN_ON_ONCE(fscrypt_decrypt_pagecache_blocks(
-					page, blocksize, bh_offset(bh)));
+			err = fscrypt_decrypt_pagecache_blocks(page, blocksize,
+							       bh_offset(bh));
+			if (err) {
+				clear_buffer_uptodate(bh);
+				goto unlock;
+			}
 		}
 	}
 	if (ext4_should_journal_data(inode)) {
-- 
2.24.1

Re: [PATCH] ext4: handle decryption error in __ext4_block_zero_page_range()

[Theodore Y. Ts'o]

On Thu, Dec 26, 2019 at 09:41:05AM -0600, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> fscrypt_decrypt_pagecache_blocks() can fail, because it uses
> skcipher_request_alloc(), which uses kmalloc(), which can fail; and also
> because it calls crypto_skcipher_decrypt(), which can fail depending on
> the driver that actually implements the crypto.
> 
> Therefore it's not appropriate to WARN on decryption error in
> __ext4_block_zero_page_range().
> 
> Remove the WARN and just handle the error instead.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Thanks, applied.

					- Ted