Re: [edk2] [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left shift
Reviewed-by: Ye Ting -Original Message- From: Wu, Hao A Sent: Thursday, September 28, 2017 12:32 PM To: edk2-devel@lists.01.org Cc: Wu, Hao A ; Shi, Steven ; Fu, Siyuan ; Ye, Ting ; Wu, Jiaxin ; Long, Qin ; Zeng, Star ; Dong, Eric ; Paolo Bonzini Subject: [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left shift 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 will remove the '~' operator before 'Time.Hour', since it seems like an implementation choice for generating the seed. Cc: Steven Shi Cc: Fu Siyuan Cc: Ye Ting Cc: Wu Jiaxin Cc: Qin Long Cc: Star Zeng Cc: Eric Dong Cc: Paolo Bonzini Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu --- 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..1ee77fe036 100644 --- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c +++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c @@ -872,7 +872,7 @@ NetRandomInitSeed ( UINT64MonotonicCount; gRT->GetTime (&Time, NULL); - Seed = (~Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | Time.Second); + Seed = (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
Re: [edk2] [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left shift
Looks good to me. Reviewed-by: Fu Siyuan -Original Message- From: Wu, Hao A Sent: Thursday, September 28, 2017 12:32 PM To: edk2-devel@lists.01.org Cc: Wu, Hao A ; Shi, Steven ; Fu, Siyuan ; Ye, Ting ; Wu, Jiaxin ; Long, Qin ; Zeng, Star ; Dong, Eric ; Paolo Bonzini Subject: [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left shift 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 will remove the '~' operator before 'Time.Hour', since it seems like an implementation choice for generating the seed. Cc: Steven Shi Cc: Fu Siyuan Cc: Ye Ting Cc: Wu Jiaxin Cc: Qin Long Cc: Star Zeng Cc: Eric Dong Cc: Paolo Bonzini Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu --- 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..1ee77fe036 100644 --- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c +++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c @@ -872,7 +872,7 @@ NetRandomInitSeed ( UINT64MonotonicCount; gRT->GetTime (&Time, NULL); - Seed = (~Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | Time.Second); + Seed = (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
Re: [edk2] [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left shift
Reviewed-by: Wu Jiaxin > -Original Message- > From: Wu, Hao A > Sent: Thursday, September 28, 2017 12:32 PM > To: edk2-devel@lists.01.org > Cc: Wu, Hao A ; Shi, Steven ; > Fu, Siyuan ; Ye, Ting ; Wu, Jiaxin > ; Long, Qin ; Zeng, Star > ; Dong, Eric ; Paolo Bonzini > > Subject: [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left > shift > > 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 will remove the '~' operator before 'Time.Hour', since it > seems like an implementation choice for generating the seed. > > Cc: Steven Shi > Cc: Fu Siyuan > Cc: Ye Ting > Cc: Wu Jiaxin > Cc: Qin Long > Cc: Star Zeng > Cc: Eric Dong > Cc: Paolo Bonzini > Contributed-under: TianoCore Contribution Agreement 1.1 > Signed-off-by: Hao Wu > --- > 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..1ee77fe036 100644 > --- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c > +++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c > @@ -872,7 +872,7 @@ NetRandomInitSeed ( >UINT64MonotonicCount; > >gRT->GetTime (&Time, NULL); > - Seed = (~Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | > Time.Second); > + Seed = (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
[edk2] [PATCH v3 4/5] MdeModulePkg/DxeNetLib: Fix negative value left shift
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 will remove the '~' operator before 'Time.Hour', since it seems like an implementation choice for generating the seed. Cc: Steven Shi Cc: Fu Siyuan Cc: Ye Ting Cc: Wu Jiaxin Cc: Qin Long Cc: Star Zeng Cc: Eric Dong Cc: Paolo Bonzini Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Hao Wu --- 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..1ee77fe036 100644 --- a/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c +++ b/MdeModulePkg/Library/DxeNetLib/DxeNetLib.c @@ -872,7 +872,7 @@ NetRandomInitSeed ( UINT64MonotonicCount; gRT->GetTime (&Time, NULL); - Seed = (~Time.Hour << 24 | Time.Day << 16 | Time.Minute << 8 | Time.Second); + Seed = (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
