[{"id":3673742,"web_url":"http://patchwork.ozlabs.org/comment/3673742/","msgid":"<87bjfw5h61.fsf@suse.de>","list_archive_url":null,"date":"2026-04-06T13:53:26","subject":"Re: [PATCH v2] migration: validate page_size in mapped-ram header\n before use","submitter":{"id":85343,"url":"http://patchwork.ozlabs.org/api/people/85343/","name":"Fabiano Rosas","email":"farosas@suse.de"},"content":"Trieu Huynh writes:\n\n> From: Trieu Huynh \n>\n> mapped_ram_read_header() reads page_size from the migration stream and\n> stores it in MappedRamHeader, but does not validate that the value is\n> non-zero before it is later used in parse_ramblock_mapped_ram():\n>\n> num_pages = length / header.page_size;\n>\n> If a corrupted or malformed migration stream provides invalid, guest\n> resumes either with corrupted memory or crashes unexpectedly (eg.\n> page_size = 0)\n>\n> Add validation in mapped_ram_read_header() to reject invalid page_size\n> values early and return an error instead of continuing with an invalid\n> header.\n>\n> Steps to reproduce:\n>\n> Create a migration snapshot with mapped-ram enabled:\n> (qemu) migrate_set_capability mapped-ram on\n> (qemu) migrate file:/tmp/qemu-snapshots/snapshot.bin\n> Modify the snapshot so that MappedRamHeader.page_size becomes diff with\n> target psize. (0/512/8192/1GB).\n> Restore the snapshot:\n> (qemu) migrate_set_capability mapped-ram on\n> (qemu) migrate_incoming file:/tmp/qemu-snapshots/snapshot.bin\n>\n> As-is:\n> * [0]: Floating point exception (core dumped)\n> * [512/8192]: Silent corruption\n> * [1GB]: \"post load hook failed for: kvm-tpr-opt\" (EPERM)\n> To-be:\n> * All: qemu-system-x86_64: Migration mapped-ram header has invalid\n> page_size [val] (expected 4096)\n>\n> Signed-off-by: Trieu Huynh \n> ---\n> v2:\n> - Replace == 0 check with != TARGET_PAGE_SIZE, which also catches\n> non-zero wrong values and matches the actual invariant of the\n> mapped-ram feature (suggested by Peter Xu)\n> - Include actual and expected values in the error message\n>\n> migration/ram.c | 6 ++++++\n> 1 file changed, 6 insertions(+)\n>\n> diff --git a/migration/ram.c b/migration/ram.c\n> index 979751f61b..2046f16caa 100644\n> --- a/migration/ram.c\n> +++ b/migration/ram.c\n> @@ -3088,6 +3088,12 @@ static bool mapped_ram_read_header(QEMUFile *file, MappedRamHeader *header,\n> }\n> \n> header->page_size = be64_to_cpu(header->page_size);\n> + if (header->page_size != TARGET_PAGE_SIZE) {\n> + error_setg(errp, \"Migration mapped-ram header has invalid \"\n> + \"page_size %\" PRIu64 \" (expected %d)\",\n> + header->page_size, TARGET_PAGE_SIZE);\n> + return false;\n> + }\n> header->bitmap_offset = be64_to_cpu(header->bitmap_offset);\n> header->pages_offset = be64_to_cpu(header->pages_offset);\n\nReviewed-by: Fabiano Rosas ","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=suse.de header.i=@suse.de header.a=rsa-sha256\n header.s=susede2_rsa header.b=lYdQyTpv;\n\tdkim=pass header.d=suse.de header.i=@suse.de header.a=ed25519-sha256\n header.s=susede2_ed25519 header.b=IURRBPJ8;\n\tdkim=pass (1024-bit key) header.d=suse.de header.i=@suse.de\n header.a=rsa-sha256 header.s=susede2_rsa header.b=fRBLfheZ;\n\tdkim=neutral header.d=suse.de header.i=@suse.de header.a=ed25519-sha256\n header.s=susede2_ed25519 header.b=ZVCaitUn;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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