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device/dram/ddr3.c: Check SPD byte before using as a divisor 

The Medium Time Base (MTB) value is calculated by dividing one SPD
byte by another. Return an error if the divisor is zero before using
the value for division.

Found-by: Coverity Scan #1469303
Signed-off-by: Martin Roth <gaumless@gmail.com>
Change-Id: Ic0a70291c42b5c2d21d65de92487b2dd88609983
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78613
Reviewed-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>
This commit is contained in:
Martin Roth 2023-10-23 17:10:29 -06:00 committed by Felix Held
parent 58964ff02c
commit a41abea65d
1 changed files with 4 additions and 0 deletions
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4
src/device/dram/ddr3.c
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@ -422,6 +422,8 @@ int spd_xmp_decode_ddr3(struct dimm_attr_ddr3_st *dimm, spd_raw_data spd,
/* Medium Timebase = /* Medium Timebase =
* Medium Timebase (MTB) Dividend / * Medium Timebase (MTB) Dividend /
* Medium Timebase (MTB) Divisor */ * Medium Timebase (MTB) Divisor */
if (spd[181] == 0) // Avoid dividing by zero.
return SPD_STATUS_INVALID;
mtb = (((u32)spd[180]) << 8) / spd[181]; mtb = (((u32)spd[180]) << 8) / spd[181];
dimm->dimms_per_channel = ((spd[178] >> 2) & 0x3) + 1; dimm->dimms_per_channel = ((spd[178] >> 2) & 0x3) + 1;
@ -437,6 +439,8 @@ int spd_xmp_decode_ddr3(struct dimm_attr_ddr3_st *dimm, spd_raw_data spd,
/* Medium Timebase = /* Medium Timebase =
* Medium Timebase (MTB) Dividend / * Medium Timebase (MTB) Dividend /
* Medium Timebase (MTB) Divisor */ * Medium Timebase (MTB) Divisor */
if (spd[183] == 0) // Avoid dividing by zero.
return SPD_STATUS_INVALID;
mtb = (((u32)spd[182]) << 8) / spd[183]; mtb = (((u32)spd[182]) << 8) / spd[183];
dimm->dimms_per_channel = ((spd[178] >> 4) & 0x3) + 1; dimm->dimms_per_channel = ((spd[178] >> 4) & 0x3) + 1;