fix: Avoid stack overflow when deserializing large flat JSON objects#5361
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fix: Avoid stack overflow when deserializing large flat JSON objects#5361
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Replace JsonObjectDeserializer's recursive token parsing with an iterative loop. The parser already tracks state explicitly, so recursion was only used to advance to the next JSON token and could overflow on large flat maps. Relates to getsentry/sentry-dart#3668
📲 Install BuildsAndroid
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vm might not respect stack size, so increase the frame count (with smaller payload) to make test more robust
buenaflor
reviewed
May 4, 2026
Comment on lines
+180
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+219
| fun `deserializes event with large flat modules map on a small stack`() { | ||
| val moduleCount = 50000 | ||
| val json = buildString { | ||
| append("{\"event_id\":\"00000000000000000000000000000000\",\"modules\":{") | ||
| repeat(moduleCount) { | ||
| if (it > 0) { | ||
| append(',') | ||
| } | ||
| append("\"m") | ||
| append(it) | ||
| append("\":\"v\"") | ||
| } | ||
| append("}}") | ||
| } | ||
|
|
||
| val error = AtomicReference<Throwable?>() | ||
| val event = AtomicReference<SentryEvent?>() | ||
| val thread = | ||
| Thread( | ||
| null, | ||
| Runnable { | ||
| try { | ||
| event.set( | ||
| JsonSerializer(SentryOptions()) | ||
| .deserialize(StringReader(json), SentryEvent::class.java) | ||
| ) | ||
| } catch (throwable: Throwable) { | ||
| error.set(throwable) | ||
| } | ||
| }, | ||
| "large-flat-modules-repro", | ||
| 1024L * 1024L, | ||
| ) | ||
|
|
||
| thread.start() | ||
| thread.join() | ||
|
|
||
| assertNull(error.get()) | ||
| assertEquals(moduleCount, event.get()?.modules?.size) | ||
| } |
Contributor
There was a problem hiding this comment.
does this test fail with the previous (recursive) variant?
Contributor
Performance metrics 🚀
|
| Revision | Plain | With Sentry | Diff |
|---|---|---|---|
| 8687935 | 294.00 ms | 304.02 ms | 10.02 ms |
| 6edfca2 | 305.52 ms | 432.78 ms | 127.26 ms |
| b6702b0 | 395.86 ms | 409.98 ms | 14.12 ms |
| a1eadfa | 345.67 ms | 411.26 ms | 65.59 ms |
| 889ecea | 367.58 ms | 437.52 ms | 69.94 ms |
| e2dce0b | 315.85 ms | 369.20 ms | 53.35 ms |
| d15471f | 322.58 ms | 396.08 ms | 73.50 ms |
| 62b579c | 349.26 ms | 426.26 ms | 77.00 ms |
| cf708bd | 434.73 ms | 502.96 ms | 68.22 ms |
| 6edfca2 | 316.43 ms | 398.90 ms | 82.46 ms |
App size
| Revision | Plain | With Sentry | Diff |
|---|---|---|---|
| 8687935 | 1.58 MiB | 2.19 MiB | 619.17 KiB |
| 6edfca2 | 1.58 MiB | 2.13 MiB | 559.07 KiB |
| b6702b0 | 1.58 MiB | 2.12 MiB | 551.79 KiB |
| a1eadfa | 0 B | 0 B | 0 B |
| 889ecea | 1.58 MiB | 2.11 MiB | 539.75 KiB |
| e2dce0b | 0 B | 0 B | 0 B |
| d15471f | 1.58 MiB | 2.13 MiB | 559.54 KiB |
| 62b579c | 0 B | 0 B | 0 B |
| cf708bd | 1.58 MiB | 2.11 MiB | 539.71 KiB |
| 6edfca2 | 1.58 MiB | 2.13 MiB | 559.07 KiB |
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📜 Description
Replace JsonObjectDeserializer's recursive token parsing with an iterative loop. The parser already tracks state explicitly, so recursion was only used to advance to the next JSON token and could overflow on large flat maps.
💡 Motivation and Context
Relates to getsentry/sentry-dart#3668
💚 How did you test it?
Added a regression test. It fails with StackOverflow before the test.
📝 Checklist
sendDefaultPIIis enabled.