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bh=YTxmdF/UnCq0KhrR2mBACaUPeFcUxBEWt7nmkQ85UmE=; b=OBZSoW/WYz9xmcPbV62WyDs+VJmZxxBYiZk4PAseCCzI2cAAaKXjsjtBFoMMvFKpsTupTV WerX09B/kx5W3crN4vTjEkurgxRZt0rH35uWSa88rZU1tsFQIsOm/vdivP/h8IOkhTfbXh hxhCs6D0BkuULRGNHI5FF7hxA3a1aQ8= X-MC-Unique: Jnd-Y3QfMPW8P3fxXm-7yQ-1 From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, stefanha@redhat.com, qemu-devel@nongnu.org Subject: [PULL 04/58] vvfat: allow some writes to bootsector Date: Thu, 27 Oct 2022 20:30:52 +0200 Message-Id: <20221027183146.463129-5-kwolf@redhat.com> In-Reply-To: <20221027183146.463129-1-kwolf@redhat.com> References: <20221027183146.463129-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 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=lists.gnu.org; Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.515, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, 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: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Qemu-devel" Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1666895694539100001 From: Herv=C3=A9 Poussineau 'reserved1' field in bootsector is used to mark volume dirty, or need to ve= rify. Allow writes to bootsector which only changes the 'reserved1' field. This fixes I/O errors on Windows guests. Resolves: https://bugs.launchpad.net/qemu/+bug/1889421 Signed-off-by: Herv=C3=A9 Poussineau Message-Id: <20221010175511.3414357-2-hpoussin@reactos.org> Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- block/vvfat.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/block/vvfat.c b/block/vvfat.c index f9bf8406d3..e76b42dbaf 100644 --- a/block/vvfat.c +++ b/block/vvfat.c @@ -2993,11 +2993,35 @@ DLOG(checkpoint()); =20 vvfat_close_current_file(s); =20 + if (sector_num =3D=3D s->offset_to_bootsector && nb_sectors =3D=3D 1) { + /* + * Write on bootsector. Allow only changing the reserved1 field, + * used to mark volume dirtiness + */ + unsigned char *bootsector =3D s->first_sectors + + s->offset_to_bootsector * 0x200; + /* + * LATER TODO: if FAT32, this is wrong (see init_directories(), + * which always creates a FAT16 bootsector) + */ + const int reserved1_offset =3D offsetof(bootsector_t, u.fat16.rese= rved1); + + for (i =3D 0; i < 0x200; i++) { + if (i !=3D reserved1_offset && bootsector[i] !=3D buf[i]) { + fprintf(stderr, "Tried to write to protected bootsector\n"= ); + return -1; + } + } + + /* Update bootsector with the only updatable byte, and return succ= ess */ + bootsector[reserved1_offset] =3D buf[reserved1_offset]; + return 0; + } + /* * Some sanity checks: * - do not allow writing to the boot sector */ - if (sector_num < s->offset_to_fat) return -1; =20 --=20 2.37.3