We still need to discuss the feasibility/need of inclusion of each fix in Xenial.
** Description changed: - Due to an issue in the kaslr address resolution in makedumpfile, we may - get the following error when collecting a dump: + [Impact] + + * Currently makedumpfile has 2 flaws due to: (a) out of synchronization + with kernel code and, (b) kaslr handling. The first is related to a + definition of a memory flag bit, whereas the second is about kaslr + offset calculation - both cause similar failures when collecting the + vmcore in kdump environment: Excluding unnecessary pages : [ 46.3 %] / __vtop4_x86_64[ 39.341233]: Can't get a valid pmd_pte. readmem: Can't convert a virtual address(ffffe05cb4000000) to physical address. readmem: type_addr: 0, addr:ffffe05cb4000000, size:32768 __exclude_unnecessary_pages: Can't read the buffer of struct page. create_2nd_bitmap: Can't exclude unnecessary pages. - This is believed to be fixed by commit: 3222d4ad04c6 ("x86_64: fix - get_kaslr_offset_x86_64() to return kaslr_offset correctly"). This LP - keeps track of Test/SRU for this commit. + * The report is mainly related to the first issue, which started to + happen after the merge of kernel commit 326e1b8f83a4 ("mm/sparsemem: + introduce a SECTION_IS_EARLY flag"), introduced in kernel 5.3. After + this commit, a memory flag was changed and induced the error in dump + collection. The fix is available in makedumpfile, as commit 7bdb468c2c + ("Increase SECTION_MAP_LAST_BIT to 4"). This is hereby SRUed to Bionic + (due to HWE kernel 5.3), Eoan and Focal. + + * The other issue is fixed in both Eoan and Focal, on makedumpfile + 1.6.6-based version. It is related with the kaslr offset: if the offset + is small enough, we may return 0 wrongly in get_kaslr_offset_x86_64(), + causing the vmcore collection to fail or even worse, to erase unintended + data from the memory dump. This is fixed by makedumpfile commit + 3222d4ad04 ("x86_64: fix get_kaslr_offset_x86_64() to return + kaslr_offset correctly"), which isn't present in versions before 1.6.6. + We hereby SRU this fix for Bionic. + + * Notice this modification is being worked concurrently with other + kdump-tools' changes in LP #1828596. + + [Test Case] + + 1) Deploy an Eoan VM e.g. with uvt-kvm; + 2) Set-up console output in the guest; + 3) Install the kdump-tools package; + 4) Configure and collect a dump (with sysrq to panic the system) - the error aforementioned is observed given Eoan kernel is 5.3-based. + + [Regression Potential] + + * The modifications hereby proposed are minimal and scope-constrained to + makedumpfile in x86_64; both are merged in makedumpfile upstream, one of + them being already released in E/F. An unlikely regression would + potentially fails vmcore collection in kdump environment. ** Changed in: makedumpfile (Ubuntu Xenial) Status: Invalid => Opinion -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1857616 Title: Cannot collect dump due to "Can't get a valid pmd_pte" error To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/makedumpfile/+bug/1857616/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs