fix(hset_family): Fix crash on scan after expiry set #4802
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When expiry is set on an hset its members are migrated to a string map. If a scan is performed on the hset, the code branch for string map accessed the value pointer directly by loading the 64 bit value from the object pointer. When creating a new entry in string map with TTL, we also set a bit on the stored pointer as metadata, this is set as 1 << 63. As a result when loading back the pointer we need to unset the same bit to get the correct address, this is done already in string map internals but the scan code did not do this, resulting in segfault. This change adds an AND operation to unset the TTL bit before dereferencing the pointer. Signed-off-by: Abhijat Malviya <[email protected]>
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romange
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Mar 20, 2025
src/core/string_map.h
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| @@ -147,6 +147,11 @@ class StringMap : public DenseSet { | |||
| void RandomPairs(unsigned int count, std::vector<sds>& keys, std::vector<sds>& vals, | |||
| bool with_value); | |||
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| static constexpr uint64_t kValTtlBit = 1ULL << 63; | |||
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there is no need to move these constants here
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Fixed, I had originally used the constant directly in hset_family.cc but now StringMap::GetValue method is used, moved these back.
Signed-off-by: Abhijat Malviya <[email protected]>
romange
reviewed
Mar 20, 2025
Signed-off-by: Abhijat Malviya <[email protected]>
romange
approved these changes
Mar 20, 2025
adiholden
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Mar 20, 2025
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When expiry is set on an hset its members are migrated to a string map.
When creating a new entry in string map with TTL, we also set a bit on the stored pointer as metadata, this is set as 1 << 63. As a consequence when reading back the pointer, if expiry is set, we need to unset the same bit to get the correct address, this is done already in string map internals.
This change adds a similar AND operation in the scan code to unset the TTL bit before dereferencing the pointer.
fixes #4799