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Sun, 05 Apr 2026 02:45:05 -0700 (PDT) From: Trieu Huynh X-Google-Original-From: Trieu Huynh To: qemu-devel@nongnu.org Cc: peterx@redhat.com, Trieu Huynh , Fabiano Rosas Subject: [PATCH v2] migration: validate page_size in mapped-ram header before use Date: Sun, 5 Apr 2026 16:44:47 +0700 Message-ID: <20260405094447.11347-1-viking4@gmail.com> 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=lists.gnu.org; Received-SPF: pass client-ip=2607:f8b0:4864:20::102a; envelope-from=vikingtc4@gmail.com; helo=mail-pj1-x102a.google.com X-Spam_score_int: -17 X-Spam_score: -1.8 X-Spam_bar: - X-Spam_report: (-1.8 / 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, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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 @gmail.com) X-ZM-MESSAGEID: 1775393258253158500 Content-Type: text/plain; charset="utf-8" From: Trieu Huynh mapped_ram_read_header() reads page_size from the migration stream and stores it in MappedRamHeader, but does not validate that the value is non-zero before it is later used in parse_ramblock_mapped_ram(): num_pages =3D length / header.page_size; If a corrupted or malformed migration stream provides invalid, guest resumes either with corrupted memory or crashes unexpectedly (eg. page_size =3D 0) Add validation in mapped_ram_read_header() to reject invalid page_size values early and return an error instead of continuing with an invalid header. Steps to reproduce: Create a migration snapshot with mapped-ram enabled: (qemu) migrate_set_capability mapped-ram on (qemu) migrate file:/tmp/qemu-snapshots/snapshot.bin Modify the snapshot so that MappedRamHeader.page_size becomes diff with target psize. (0/512/8192/1GB). Restore the snapshot: (qemu) migrate_set_capability mapped-ram on (qemu) migrate_incoming file:/tmp/qemu-snapshots/snapshot.bin As-is: * [0]: Floating point exception (core dumped) * [512/8192]: Silent corruption * [1GB]: "post load hook failed for: kvm-tpr-opt" (EPERM) To-be: * All: qemu-system-x86_64: Migration mapped-ram header has invalid page_size [val] (expected 4096) Signed-off-by: Trieu Huynh Reviewed-by: Fabiano Rosas --- v2: - Replace =3D=3D 0 check with !=3D TARGET_PAGE_SIZE, which also catches non-zero wrong values and matches the actual invariant of the mapped-ram feature (suggested by Peter Xu) - Include actual and expected values in the error message migration/ram.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/migration/ram.c b/migration/ram.c index 979751f61b..2046f16caa 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -3088,6 +3088,12 @@ static bool mapped_ram_read_header(QEMUFile *file, M= appedRamHeader *header, } =20 header->page_size =3D be64_to_cpu(header->page_size); + if (header->page_size !=3D TARGET_PAGE_SIZE) { + error_setg(errp, "Migration mapped-ram header has invalid " + "page_size %" PRIu64 " (expected %d)", + header->page_size, TARGET_PAGE_SIZE); + return false; + } header->bitmap_offset =3D be64_to_cpu(header->bitmap_offset); header->pages_offset =3D be64_to_cpu(header->pages_offset); =20 --=20 2.43.0