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Tue, 09 Jun 2026 19:33:43 -0700 (PDT) From: Christian Barry X-Google-Original-From: Christian Barry To: qemu-devel@nongnu.org Cc: Kevin Wolf , Eric Blake , John Snow , qemu-block@nongnu.org, Hanna Reitz , David de Barros Tadokoro , Vladimir Sementsov-Ogievskiy , Christian Barry , Eduardo Augusto Cavalcanti Subject: [PATCH] block: qcow2-bitmap: fix persistent bitmap corruption on ENOSPC Date: Tue, 9 Jun 2026 23:33:37 -0300 Message-ID: <20260610023337.165474-1-christian.barry@usp.br> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists1p.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::931; envelope-from=christian.barry@usp.br; helo=mail-ua1-x931.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @usp.br) X-ZM-MESSAGEID: 1781058882994158500 Content-Type: text/plain; charset="utf-8" From: Christian Barry Changed qcow2_co_remove_persistent_dirty_bitmap() to treat free_bitmap_clus= ters() failure as fatal and roll back the header update through a new helper function rollback_ext_header_and_dir_helper(), which was also applied to update_ext_header_and_dir(), which had internal rollback logic. Changed bitmap_list_store() to zero the cluster tail after write, guaranteeing that qemu-img won't parse into stale bytes. Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3516 Signed-off-by: Christian Barry Co-developed by: Eduardo Augusto Cavalcanti Signed-off-by: Eduardo Augusto Cavalcanti --- block/qcow2-bitmap.c | 37 ++++++++++++++++++++++++++++++++----- 1 file changed, 32 insertions(+), 5 deletions(-) diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c index 256ec99878..5796298157 100644 --- a/block/qcow2-bitmap.c +++ b/block/qcow2-bitmap.c @@ -737,10 +737,12 @@ static int GRAPH_RDLOCK bitmap_list_store(BlockDriverState *bs, Qcow2BitmapList *bm_list, uint64_t *offset, uint64_t *size, bool in_place) { + BDRVQcow2State *s =3D bs->opaque; int ret; uint8_t *dir; int64_t dir_offset =3D 0; uint64_t dir_size =3D 0; + uint64_t tail_size; Qcow2Bitmap *bm; Qcow2BitmapDirEntry *e; =20 @@ -810,6 +812,14 @@ bitmap_list_store(BlockDriverState *bs, Qcow2BitmapLis= t *bm_list, goto fail; } =20 + tail_size =3D ROUND_UP(dir_size, s->cluster_size) - dir_size; + if (tail_size > 0) { + ret =3D bdrv_pwrite_zeroes(bs->file, dir_offset + dir_size, tail_s= ize, 0); + if (ret < 0) { + goto fail; + } + } + g_free(dir); =20 if (!in_place) { @@ -882,6 +892,19 @@ update_ext_header_and_dir_in_place(BlockDriverState *b= s, */ } =20 +static void rollback_ext_header_and_dir_helper(BlockDriverState *bs, + uint64_t old_offset, + uint64_t old_size, + uint32_t old_nb_bitmaps, + uint64_t old_autocl) +{ + BDRVQcow2State *s =3D bs->opaque; + s->bitmap_directory_offset =3D old_offset; + s->bitmap_directory_size =3D old_size; + s->nb_bitmaps =3D old_nb_bitmaps; + s->autoclear_features =3D old_autocl; +} + static int GRAPH_RDLOCK update_ext_header_and_dir(BlockDriverState *bs, Qcow2BitmapList *bm_list) { @@ -937,10 +960,7 @@ fail: qcow2_free_clusters(bs, new_offset, new_size, QCOW2_DISCARD_OTHER); } =20 - s->bitmap_directory_offset =3D old_offset; - s->bitmap_directory_size =3D old_size; - s->nb_bitmaps =3D old_nb_bitmaps; - s->autoclear_features =3D old_autocl; + rollback_ext_header_and_dir_helper(bs, old_offset, old_size, old_nb_bi= tmaps, old_autocl); =20 return ret; } @@ -1460,6 +1480,10 @@ int coroutine_fn qcow2_co_remove_persistent_dirty_bi= tmap(BlockDriverState *bs, { int ret; BDRVQcow2State *s =3D bs->opaque; + uint64_t old_offset =3D s->bitmap_directory_offset; + uint64_t old_size =3D s->bitmap_directory_size; + uint32_t old_nb_bitmaps =3D s->nb_bitmaps; + uint64_t old_autocl =3D s->autoclear_features; Qcow2Bitmap *bm =3D NULL; Qcow2BitmapList *bm_list; =20 @@ -1495,7 +1519,10 @@ int coroutine_fn qcow2_co_remove_persistent_dirty_bi= tmap(BlockDriverState *bs, goto out; } =20 - free_bitmap_clusters(bs, &bm->table); + ret =3D free_bitmap_clusters(bs, &bm->table); + if (ret < 0){ + rollback_ext_header_and_dir_helper(bs, old_offset, old_size, old_nb_bitma= ps, old_autocl); + } =20 out: qemu_co_mutex_unlock(&s->lock); --=20 2.43.0