crypto: ecdsa - Harden against integer overflows in DIV_ROUND_UP()

Summary

In the Linux kernel, the following vulnerability has been resolved: crypto: ecdsa - Harden against integer overflows in DIV_ROUND_UP() Herbert notes that DIV_ROUND_UP() may overflow unnecessarily if an ecdsa implementation's ->key_size() callback returns an unusually large value. Herbert instead suggests (for a division by 8): X / 8 + !!(X & 7) Based on this formula, introduce a generic DIV_ROUND_UP_POW2() macro and use it in lieu of DIV_ROUND_UP() for ->key_size() return values. Additionally, use the macro in ecc_digits_from_bytes(), whose "nbytes" parameter is a ->key_size() return value in some instances, or a user-specified ASN.1 length in the case of ecdsa_get_signature_rs().

Timeline

1. May 20, 2025, 5:09 PM UTCCVE published
2. Oct 15, 2026, 9:46 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 15, 2026, 9:52 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 55779f26eab9af12474a447001bd17070f055712 · fixed in f02f0218be412cff1c844addf58e002071be298b; From c6ab5c915da460c0397960af3c308386c3f3247b · fixed in f2133b849ff273abddb6da622daddd8f6f6fa448; From c6ab5c915da460c0397960af3c308386c3f3247b · fixed in 921b8167f10708e38080f84e195cdc68a7a561f1; From c6ab5c915da460c0397960af3c308386c3f3247b · fixed in b16510a530d1e6ab9683f04f8fb34f2e0f538275; From 6.6.70 · fixed in 6.6.99

• Linux Linux

  6.10

• KernelLinux

  fixed in 6.6.99; From 6.7.0 · fixed in 6.12.39; From 6.10.0 · fixed in 6.14.5

References 4