REF: https://bugzilla.tianocore.org/show_bug.cgi?id=698
Within function NetRandomInitSeed(), left shift a negative value is used in: "~Time.Hour << 24" which involves undefined behavior. Since Time.Hour is of type UINT8 (range from 0 to 23), hence ~Time.Hour will be a negative value (of type int, signed). According to the C11 spec, Section 6.5.7: > 4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated > bits are filled with zeros. If E1 has an unsigned type, the value > of the result is E1 * 2^E2 , reduced modulo one more than the > maximum value representable in the result type. If E1 has a signed > type and nonnegative value, and E1 * 2^E2 is representable in the > result type, then that is the resulting value; otherwise, the > behavior is undefined. This commit explicitly cast 'Time.Hour' with UINT32 to resolve this issue. Cc: Steven Shi <steven....@intel.com> Cc: Fu Siyuan <siyuan...@intel.com> Cc: Ye Ting <ting...@intel.com> Cc: Wu Jiaxin <jiaxin...@intel.com> Cc: Star Zeng <star.z...@intel.com> Cc: Eric Dong <eric.d...@intel.com> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu <hao.a...@intel.com> --- MdeModulePkg/Library/DxeNetLib/DxeNetLib.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c index 7cd7e3aca0..ca5413edcc 100644 --- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c +++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c @@ -872,7 +872,7 @@ NetRandomInitSeed ( UINT64 MonotonicCount; gRT->GetTime (&Time, NULL); - Seed = (~Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | Time.Second); + Seed = (~(UINT32)Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | Time.Second); Seed ^= Time.Nanosecond; Seed ^= Time.Year << 7; -- 2.12.0.windows.1 _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
