From: usa@... Date: 2019-08-26T15:59:05+00:00 Subject: [ruby-core:94575] [Ruby master Bug#15792] GC can leave strings used as hash keys in a corrupted state Issue #15792 has been updated by usa (Usaku NAKAMURA). Backport changed from 2.4: REQUIRED, 2.5: REQUIRED, 2.6: DONE to 2.4: REQUIRED, 2.5: DONE, 2.6: DONE ruby_2_5 r67766 merged revision(s) 3f9562015e651735bfc2fdd14e8f6963b673e22a,c06ddfee878524168e4af07443217ed2f8d0954b,3b3b4a44e5. ---------------------------------------- Bug #15792: GC can leave strings used as hash keys in a corrupted state https://bugs.ruby-lang.org/issues/15792#change-81033 * Author: byroot (Jean Boussier) * Status: Closed * Priority: Normal * Assignee: * Target version: * ruby -v: 2.6.2 * Backport: 2.4: REQUIRED, 2.5: DONE, 2.6: DONE ---------------------------------------- The following script showcase the issue: ``` #!/usr/bin/env ruby --disable-gems a = ('a' * 24).encode(Encoding::ASCII).gsub('x', '') b = ('b' * 24).encode(Encoding::ASCII).gsub('x', '') hash = {} hash[a] = true hash[b] = true puts "Bebore garbage_collection: a=#{a.inspect} b=#{b.inspect}" 4.times { GC.start } puts "After garbage_collection: a=#{a.inspect} b=#{b.inspect}" ``` Expected output: ``` Bebore garbage_collection: a="aaaaaaaaaaaaaaaaaaaaaaaa" b="bbbbbbbbbbbbbbbbbbbbbbbb" After garbage_collection: a="aaaaaaaaaaaaaaaaaaaaaaaa" b="bbbbbbbbbbbbbbbbbbbbbbbb" ``` Actual output: ``` Ruby: 2.6.2 Bebore garbage_collection: a="aaaaaaaaaaaaaaaaaaaaaaaa" b="bbbbbbbbbbbbbbbbbbbbbbbb" After garbage_collection: a="}\x0Eu\xDB\xFC\a\x00\x80\xE9\ru\xDB\xFC\a\x00\x10\x04\x00aaaaaa" b="\x00\x00\x00\x00\x00\x00\x00\xC0\x00\x00\x00\x00\x00\x00\x00\xC0\x02\x00bbbbbb" ``` We reduced the repro script as much as we could, both the `.encode(ASCII)` and the `gsub` are necessary for the bug to manifest itself. We also used `ObjectSpace.dump()` to analyze the corrupted string. ``` b = "shared":true, "encoding":"US-ASCII", "references":["0x7faf4a01aeb8"] 0x7faf4a01aeb8 = "frozen":true, "fstring":true, "bytesize":24, "value":"bbbbbbbbbbbbbbbbbbbbbbbb", "encoding":"US-ASCII" ``` Big thanks to �douard Chin who did most of the initial repro reduction. -- https://bugs.ruby-lang.org/ Unsubscribe: