Fix CSN1 decoding: CSN_LEFT_ALIGNED_VAR_BMP bounds
Fix attempted read past vector boundaries in case of a starting bit offset != 0, so that the last amount of bits read should be < 8. In the case of CSN_LEFT_ALIGNED_VAR_BMP, the mod-8 calculation was flawed, and in the final step, 8 bits were read instead of the remainder < 8. This lead to -EINVAL being returned by bitvec_get_bit_pos() and bogus resulting data. Instead, read 8 bits only as long as at least 8 bits remain, and read any remaining bits < 8 in a final step. Drop unneeded nB1 variable and an obvious comment. Adjust the unit test assertion in testCsnLeftAlignedVarBmpBounds() in RLCMACTest.cpp. Based on a fix by Aravind Sirsikar <Arvind.Sirsikar@radisys.com>, but implemented differently. Related: OS#1805 Change-Id: I490498c8da6b531f54acb673379379f7b10907c0
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11
src/csn1.cpp
11
src/csn1.cpp
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@ -1110,22 +1110,21 @@ csnStreamDecoder(csnStream_t* ar, const CSN_DESCR* pDescr, bitvec *vector, unsig
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{ /* extract bits */
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guint8* pui8 = pui8DATA(data, pDescr->offset);
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gint16 nB1 = no_of_bits & 0x07;/* no_of_bits Mod 8 */
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while (no_of_bits > 0)
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while (no_of_bits >= 8)
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{
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*pui8 = bitvec_read_field(vector, readIndex, 8);
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LOGPC(DCSN1, LOGL_NOTICE, "%s = %u | ", pDescr->sz , (unsigned)*pui8);
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pui8++;
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no_of_bits -= 8;
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}
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if (nB1 > 0)
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if (no_of_bits > 0)
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{
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*pui8 = bitvec_read_field(vector, readIndex, nB1);
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*pui8 = bitvec_read_field(vector, readIndex, no_of_bits);
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LOGPC(DCSN1, LOGL_NOTICE, "%s = %u | ", pDescr->sz , (unsigned)*pui8);
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pui8++;
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no_of_bits -= nB1;
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bit_offset += nB1; /* (nB1 is no_of_bits Mod 8) */
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bit_offset += no_of_bits;
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no_of_bits = 0;
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}
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}
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}
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@ -223,13 +223,8 @@ void testCsnLeftAlignedVarBmpBounds()
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&data.u.Egprs_Packet_Downlink_Ack_Nack.EGPRS_AckNack.Desc;
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decode_gsm_rlcmac_uplink(vector, &data);
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/*
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* TODO: URBB len is decoded as 102 bits. So 96 + 6 bits = 12 bytes + 6
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* bits should be decoded. The 13th byte should end up as 0x00, but we
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* see data coming from bitvec_get_bit_pos() returning -EINVAL.
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*/
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OSMO_ASSERT(!strcmp(osmo_hexdump(urbb->URBB, 13),
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"7f ff ff ee 00 00 00 00 00 00 00 00 ea "));
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"7f ff ff ee 00 00 00 00 00 00 00 00 00 "));
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}
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int main(int argc, char *argv[])
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