Change in osmo-tetra[master]: Make viterbi decoder deterministic in case of bit errors / too few sy...

[Harald Welte]

Harald Welte has submitted this change and it was merged. ( https://gerrit.osmocom.org/10097 )

Change subject: Make viterbi decoder deterministic in case of bit errors / too few symbols
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Make viterbi decoder deterministic in case of bit errors / too few symbols

Running tetra-rx on a capture with lots of bit errors is not
deterministic. Investigation with Valgrind shows various errors about
uninitialised values in libosmocore's viterbi decoder.

The cause appears to lie in @lower_mac/viterbi.c at . The only function
there allocates space for 864 symbols and then fills it with the symbols
received. However, sym_count is sometimes less than 864, leaving the
rest of the array uninitialized.

Initializing it with @int8_t vit_inp[864*4] = {0};@ fixes the problem.

Change-Id: Ib745c387e21fb81afef69efcf7e46d5d49331c8f
Fixes: OS#3410
---
M src/lower_mac/viterbi.c
1 file changed, 1 insertion(+), 1 deletion(-)

Approvals:
  Jenkins Builder: Verified
  Harald Welte: Looks good to me, approved



diff --git a/src/lower_mac/viterbi.c b/src/lower_mac/viterbi.c
index 86aff77..b6f12c1 100644
--- a/src/lower_mac/viterbi.c
+++ b/src/lower_mac/viterbi.c
@@ -5,7 +5,7 @@
 
 void viterbi_dec_sb1_wrapper(const uint8_t *in, uint8_t *out, unsigned int sym_count)
 {
-	int8_t vit_inp[864*4];
+	int8_t vit_inp[864*4] = {0};
 	int i;
 
 	for (i = 0; i < sym_count*4; i++) {

-- 
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Gerrit-Project: osmo-tetra
Gerrit-Branch: master
Gerrit-MessageType: merged
Gerrit-Change-Id: Ib745c387e21fb81afef69efcf7e46d5d49331c8f
Gerrit-Change-Number: 10097
Gerrit-PatchSet: 1
Gerrit-Owner: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Jenkins Builder
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