Re: [edk2-devel] [edk2-libc Patch 1/1] edk2-libc/StdLib: Fix uninitialized global variable

[Michael Brown]

On 25/07/2023 17:07, Jayaprakash, N wrote:

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4506

res_init() is called from different places in sockets library. It depends
on global _res variable containing a state.

The problem is that if __BIND_RES_TEXT macro is not defined, _res is not
initialized. Depending on compiler and build optimization this can fill the
variable with garbage that is later used by res_init().

Fix is trivial - explicitly initialize _res.
  
  struct __res_state _res

-# if defined(__BIND_RES_TEXT)
+#if defined(__BIND_RES_TEXT)
  = { RES_TIMEOUT, }  /* Motorola, et al. */
-# endif
+#endif
+= {0}
+#endif
  ;


NAK.  This is very wrong.

Firstly, your patch introduces unnecessary whitespace changes and so is 
unnecessarily cumbersome to review.


Secondly, the patch creates an invalid "#if ... #endif ... #endif" 
combination.  I suspect that you meant to use "#else" in the middle.


Thirdly, and most importantly, the whole patch is entirely unnecessary. 
As a variable with static storage duration, if no explicit initializer 
is provided then the C language guarantees that the value will be 
initialized to zero anyway.


Thanks,

Michael



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[edk2-devel] [edk2-libc Patch 1/1] edk2-libc/StdLib: Fix uninitialized global variable

[Jayaprakash, N]

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4506

res_init() is called from different places in sockets library. It depends
on global _res variable containing a state.

The problem is that if __BIND_RES_TEXT macro is not defined, _res is not
initialized. Depending on compiler and build optimization this can fill the
variable with garbage that is later used by res_init().

Fix is trivial - explicitly initialize _res.

Cc: Rebecca Cran 
Cc: Michael D Kinney 
Cc: Jayaprakash N 
Signed-off-by: Kloper Dimitry 
---
 StdLib/BsdSocketLib/res_init.c | 6 --
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/StdLib/BsdSocketLib/res_init.c b/StdLib/BsdSocketLib/res_init.c
index 613a76a..faf2b5e 100644
--- a/StdLib/BsdSocketLib/res_init.c
+++ b/StdLib/BsdSocketLib/res_init.c
@@ -121,9 +121,11 @@ static u_int32_t net_mask __P((struct in_addr));
  */
 
 struct __res_state _res
-# if defined(__BIND_RES_TEXT)
+#if defined(__BIND_RES_TEXT)
 = { RES_TIMEOUT, }  /* Motorola, et al. */
-# endif
+#endif
+= {0}
+#endif
 ;
 
 
-- 
2.40.0.windows.1



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