fix: validate key count before allocating result in keyspec#3598
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Signed-off-by: Jacob Murphy <jkmurphy@google.com>
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## unstable #3598 +/- ##
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- Coverage 76.61% 76.52% -0.09%
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Files 160 160
Lines 80472 80471 -1
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- Hits 61652 61580 -72
- Misses 18820 18891 +71
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madolson
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Apr 30, 2026
lucasyonge
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In `getKeysUsingKeySpecs`, when extracting keys based on the `KSPEC_FK_KEYNUM `spec (like in the `EVAL` command), the server read the number of keys from the arguments and calculated the expected end index. However, it called `getKeysPrepareResult` to allocate memory for the result array before validating whether last was within the bounds of the actual arguments provided. If a client sent a command with a huge declared number of keys (e.g., `COMMAND GETKEYS EVAL "return 1" 2147483647 key1`), the server would allocate a massive amount of memory. Since `vm.overcommit_memory` is recommended, this allocation would NOT normally have triggered OOM (we never wrote to it so there is no physical memory allocated), but if you disable overcommit, this could trigger an OOM. You can reproduce it with: ``` $ prlimit --as=1073741824 src/valkey-server --save "" ... 384270:M 30 Apr 2026 04:27:24.456 * Ready to accept connections tcp ... <in valkey-cli> 127.0.0.1:6379> command getkeys eval "return 1" 2147483647 key1 ... <in server log> 384270:M 30 Apr 2026 04:29:26.950 # Out Of Memory allocating 17179869176 bytes! ``` ## Solution * Moved the bounds check `if (last >= argc || last < first || first >= argc)` to execute before the call to `getKeysPrepareResult`, preventing the large allocation on invalid input. * To further catch issues like this, protected against integer overflow during the calculation of last by using a long long temporary variable. If it exceeds INT_MAX or falls below INT_MIN, the spec is marked invalid immediately. Signed-off-by: Jacob Murphy <jkmurphy@google.com>
lucasyonge
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May 12, 2026
In `getKeysUsingKeySpecs`, when extracting keys based on the `KSPEC_FK_KEYNUM `spec (like in the `EVAL` command), the server read the number of keys from the arguments and calculated the expected end index. However, it called `getKeysPrepareResult` to allocate memory for the result array before validating whether last was within the bounds of the actual arguments provided. If a client sent a command with a huge declared number of keys (e.g., `COMMAND GETKEYS EVAL "return 1" 2147483647 key1`), the server would allocate a massive amount of memory. Since `vm.overcommit_memory` is recommended, this allocation would NOT normally have triggered OOM (we never wrote to it so there is no physical memory allocated), but if you disable overcommit, this could trigger an OOM. You can reproduce it with: ``` $ prlimit --as=1073741824 src/valkey-server --save "" ... 384270:M 30 Apr 2026 04:27:24.456 * Ready to accept connections tcp ... <in valkey-cli> 127.0.0.1:6379> command getkeys eval "return 1" 2147483647 key1 ... <in server log> 384270:M 30 Apr 2026 04:29:26.950 # Out Of Memory allocating 17179869176 bytes! ``` ## Solution * Moved the bounds check `if (last >= argc || last < first || first >= argc)` to execute before the call to `getKeysPrepareResult`, preventing the large allocation on invalid input. * To further catch issues like this, protected against integer overflow during the calculation of last by using a long long temporary variable. If it exceeds INT_MAX or falls below INT_MIN, the spec is marked invalid immediately. Signed-off-by: Jacob Murphy <jkmurphy@google.com>
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In
getKeysUsingKeySpecs, when extracting keys based on theKSPEC_FK_KEYNUMspec (like in theEVALcommand), the server read the number of keys from the arguments and calculated the expected end index.However, it called
getKeysPrepareResultto allocate memory for the result array before validating whether last was within the bounds of the actual arguments provided.If a client sent a command with a huge declared number of keys (e.g.,
COMMAND GETKEYS EVAL "return 1" 2147483647 key1), the server would allocate a massive amount of memory. Sincevm.overcommit_memoryis recommended, this allocation would NOT normally have triggered OOM (we never wrote to it so there is no physical memory allocated), but if you disable overcommit, this could trigger an OOM.You can reproduce it with:
Solution
if (last >= argc || last < first || first >= argc)to execute before the call togetKeysPrepareResult, preventing the large allocation on invalid input.