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coredump: fix handling of num_pages #2815

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coredump: fix handling of num_pages #2815

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6 changes: 5 additions & 1 deletion coredump/criu_coredump/coredump.py
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Original file line number Diff line number Diff line change
Expand Up @@ -794,7 +794,11 @@ def _get_page(self, pid, page_no):
off = 0 # in pages
for m in pagemap[1:]:
found = False
num_pages = m.get("nr_pages", m.compat_nr_pages)
num_pages = m.get("nr_pages", m.get("compat_nr_pages"))

if num_pages is None:
raise ValueError("num_pages and compat_nr_pages are missing")
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@avagin avagin Nov 9, 2025

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how is it possible? cmpat_nr_pages is a required field:

criu/images/pagemap.proto

Line 13 in e879d69

required uint32 compat_nr_pages = 2;

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@rst0git rst0git Nov 9, 2025 •
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The error appears in the CentOS Stream 9 based test CI test for the master branch (https://cirrus-ci.com/task/4855368628568064) and I was able to replicate it locally:

$ sudo crit show test/others/criu-coredump/pagemap-44763.img
{
    "magic": "PAGEMAP",
    "entries": [
        {
            "pages_id": 1
        },
        {
            "vaddr": "0x400000",
            "compat_nr_pages": 0,
            "flags": "PE_PRESENT",
            "nr_pages": 1
        },
        {
            "vaddr": "0x402000",
            "compat_nr_pages": 0,
            "flags": "PE_PRESENT",
            "nr_pages": 2
        },
        {
            "vaddr": "0x7fe251884000",
            "compat_nr_pages": 0,
            "flags": "PE_PRESENT",
            "nr_pages": 2
        },
        {
            "vaddr": "0x7fe251a6b000",
            "compat_nr_pages": 0,
            "flags": "PE_PRESENT",
            "nr_pages": 7
        },
        {
            "vaddr": "0x7fe251a75000",
            "compat_nr_pages": 0,
            "flags": "PE_PRESENT",
            "nr_pages": 4
        },
        {
            "vaddr": "0x7fe251a96000",
            "compat_nr_pages": 0,
            "flags": "PE_PRESENT",
            "nr_pages": 2
        },
        {
            "vaddr": "0x7fe251a9e000",
            "compat_nr_pages": 0,
            "flags": "PE_PRESENT",
            "nr_pages": 2
        },
        {
            "vaddr": "0x7fe251ad4000",
            "compat_nr_pages": 0,
            "flags": "PE_PRESENT",
            "nr_pages": 4
        },
        {
            "vaddr": "0x7fffaf010000",
            "compat_nr_pages": 0,
            "flags": "PE_PRESENT",
            "nr_pages": 4
        }
    ]
}

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@rst0git rst0git Nov 9, 2025 •
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In this case m is a dictionary, so m['compat_nr_pages'] works but m.compat_nr_pages does not.

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@avagin avagin Nov 9, 2025

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should we use m['compat_nr_pages']?


for i in range(num_pages):
if m["vaddr"] + i * PAGESIZE == page_no * PAGESIZE:
found = True
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