Through code search on file "pdfium_page.cc" seeing some recent changes to the file by @thestig 

Possible suspect::
https://chromium.googlesource.com/chromium/src/+/ccb5fc8ff322c02db30604d0df003626eaff5f34%5E%21/

thestig@ could you please look into this issue if it is related to your change,else please route this to an appropriate owner for this issue.

Thanks,

r421370

ClusterFuzz has detected this issue as fixed in range 421240:421431.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=5150145832550400

Fuzzer: ochang_search_index_mutator
Job Type: linux_ubsan_chrome
Platform Id: linux

Crash Type: Integer-overflow
Crash Address: 
Crash State:
  chrome_pdf::PDFiumPage::PageToScreen
  chrome_pdf::PDFiumPage::GetLink
  chrome_pdf::PDFiumPage::GetCharIndex
  
Regressed: https://cluster-fuzz.appspot.com/revisions?job=linux_ubsan_chrome&range=410916:411073
Fixed: https://cluster-fuzz.appspot.com/revisions?job=linux_ubsan_chrome&range=421240:421431

Minimized Testcase (264.13 Kb): https://cluster-fuzz.appspot.com/download/AMIfv94mQBe0TAwJV0MMlMuazHFWAhI2D5b7ZrStryHtUED_A5ajehv0TvvpC1ba4KUCr_q66e4B0Y_AypCJJxbSslZ-zrcegHUp-tAozNlgLgbAWasQa20c9OnEJp6FN7u7r6L_R7acJWHh_-XndPhpJzwEjPh7W87L4svqsEVA4GB3VrwZDiQ?testcase_id=5150145832550400

Additional requirements: Requires Gestures

See https://dev.chromium.org/Home/chromium-security/bugs/reproducing-clusterfuzz-bugs for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7253c367c1fdf94da3b299f13c6140b815b72da3

commit 7253c367c1fdf94da3b299f13c6140b815b72da3
Author: thestig <thestig@chromium.org>
Date: Tue Sep 27 22:47:13 2016

Sanitize values in chrome_pdf::PDFiumPage::PageToScreen().

BUG= 650167 

Review-Url: https://codereview.chromium.org/2374643002
Cr-Commit-Position: refs/heads/master@{#421370}

[modify] https://crrev.com/7253c367c1fdf94da3b299f13c6140b815b72da3/pdf/pdfium/pdfium_page.cc

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