From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Tue, 25 Mar 2025 15:40:35 +0000 (-0400)
Subject: bcachefs: Fix nonce inconsistency in bch2_write_prep_encoded_data()
X-Git-Tag: v6.15-rc1~83^2~34
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5af61dbd96275e184adcfe615507b0f04ed7b328;p=thirdparty%2Fkernel%2Flinux.git

bcachefs: Fix nonce inconsistency in bch2_write_prep_encoded_data()

If we're moving an extent that was partially overwritten,
bch2_write_rechecksum() will trim it to the currenty live range.

If we then also want to compress it, it'll be decrypted - but the nonce
has been advanced for the overwritten start of the extent that we
dropped, and we were using the nonce we calculated before rechecksum().

Reported-by: Gabriel de Perthuis <g2p.code@gmail.com>
Fixes: 127d90d2823e ("bcachefs: bch2_write_prep_encoded_data() now returns errcode")
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---

diff --git a/fs/bcachefs/io_write.c b/fs/bcachefs/io_write.c
index 29671075e3f1d..14c5c5c98d51d 100644
--- a/fs/bcachefs/io_write.c
+++ b/fs/bcachefs/io_write.c
@@ -839,7 +839,6 @@ static noinline int bch2_write_prep_encoded_data(struct bch_write_op *op, struct
 {
 	struct bch_fs *c = op->c;
 	struct bio *bio = &op->wbio.bio;
-	struct nonce nonce = extent_nonce(op->version, op->crc);
 	int ret = 0;
 
 	BUG_ON(bio_sectors(bio) != op->crc.compressed_size);
@@ -866,6 +865,7 @@ static noinline int bch2_write_prep_encoded_data(struct bch_write_op *op, struct
 	 */
 	if (crc_is_compressed(op->crc)) {
 		/* Last point we can still verify checksum: */
+		struct nonce nonce = extent_nonce(op->version, op->crc);
 		struct bch_csum csum = bch2_checksum_bio(c, op->crc.csum_type, nonce, bio);
 		if (bch2_crc_cmp(op->crc.csum, csum) && !c->opts.no_data_io)
 			goto csum_err;
@@ -905,6 +905,7 @@ static noinline int bch2_write_prep_encoded_data(struct bch_write_op *op, struct
 	 */
 	if (bch2_csum_type_is_encryption(op->crc.csum_type) &&
 	    (op->compression_opt || op->crc.csum_type != op->csum_type)) {
+		struct nonce nonce = extent_nonce(op->version, op->crc);
 		struct bch_csum csum = bch2_checksum_bio(c, op->crc.csum_type, nonce, bio);
 		if (bch2_crc_cmp(op->crc.csum, csum) && !c->opts.no_data_io)
 			goto csum_err;