Fix panic and OOM in repeatString for large repeat counts#2644
Merged
mikefarah merged 1 commit intomikefarah:masterfrom Apr 6, 2026
Merged
Fix panic and OOM in repeatString for large repeat counts#2644mikefarah merged 1 commit intomikefarah:masterfrom
mikefarah merged 1 commit intomikefarah:masterfrom
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The existing check (count > 10 million) does not account for string length. A 68-byte string repeated 35 trillion times passes the count check but panics in strings.Repeat with "makeslice: len out of range". Smaller counts (e.g. 10 million * 6-byte string = 60 MB) cause OOM on memory-constrained environments like OSS-Fuzz (2560 MB limit). Replace the count-only check with a result size check: the product of string length and repeat count must not exceed 10 MiB. Use division (len > limit/count) instead of multiplication (len*count > limit) to avoid integer overflow — a large count can wrap the product to a negative value, bypassing the guard entirely. Fixes at least four OSS-Fuzz bugs found via Lima's FuzzEvaluateExpression: https://issues.oss-fuzz.com/issues/418818862 (makeslice overflow) https://issues.oss-fuzz.com/issues/422001683 (timeout from huge alloc) https://issues.oss-fuzz.com/issues/383195001 (OOM, 3 GB allocation) https://issues.oss-fuzz.com/issues/385180606 (OOM, 97 TB allocation) Signed-off-by: Jan Dubois <jan@jandubois.com> Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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The existing check (count > 10 million) does not account for string length. A 68-byte string repeated 35 trillion times passes the count check but panics in strings.Repeat with "makeslice: len out of range". Smaller counts (e.g. 10 million * 6-byte string = 60 MB) cause OOM on memory-constrained environments like OSS-Fuzz (2560 MB limit).
Replace the count-only check with a result size check: the product of string length and repeat count must not exceed 10 MiB. Use division (len > limit/count) instead of multiplication (len*count > limit) to avoid integer overflow — a large count can wrap the product to a negative value, bypassing the guard entirely.
Fixes at least four OSS-Fuzz bugs found via Lima's FuzzEvaluateExpression:
https://issues.oss-fuzz.com/issues/418818862 (makeslice overflow)
https://issues.oss-fuzz.com/issues/422001683 (timeout from huge alloc)
https://issues.oss-fuzz.com/issues/383195001 (OOM, 3 GB allocation)
https://issues.oss-fuzz.com/issues/385180606 (OOM, 97 TB allocation)