libnvdimm: fix ars_status output length calculation

stellarhopper · davejiang · commit 286e87718103 · 2018-08-20T08:56:38.000-07:00
Commit efda1b5 ("acpi, nfit, libnvdimm: fix / harden ars_status output length handling") Introduced additional hardening for ambiguity in the ACPI spec for ars_status output sizing. However, it had a couple of cases mixed up. Where it should have been checking for (and returning) "out_field[1] - 4" it was using "out_field[1] - 8" and vice versa. This caused a four byte discrepancy in the buffer size passed on to the command handler, and in some cases, this caused memory corruption like: ./daxdev-errors.sh: line 76: 24104 Aborted (core dumped) ./daxdev-errors $busdev $region malloc(): memory corruption Program received signal SIGABRT, Aborted. [...] #5 0x00007ffff7865a2e in calloc () from /lib64/libc.so.6 torvalds#6 0x00007ffff7bc2970 in ndctl_bus_cmd_new_ars_status (ars_cap=ars_cap@entry=0x6153b0) at ars.c:136 torvalds#7 0x0000000000401644 in check_ars_status (check=0x7fffffffdeb0, bus=0x604c20) at daxdev-errors.c:144 torvalds#8 test_daxdev_clear_error (region_name=<optimized out>, bus_name=<optimized out>) at daxdev-errors.c:332 Cc: <stable@vger.kernel.org> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Keith Busch <keith.busch@intel.com> Cc: Lukasz Dorau <lukasz.dorau@intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Fixes: efda1b5 ("acpi, nfit, libnvdimm: fix / harden ars_status output length handling") Signed-off-by: Vishal Verma <vishal.l.verma@intel.com> Reviewed-by: Keith Busch <keith.busch@intel.com> Signed-of-by: Dave Jiang <dave.jiang@intel.com>
diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
@@ -812,9 +812,9 @@ u32 nd_cmd_out_size(struct nvdimm *nvdimm, int cmd,
 		 * overshoots the remainder by 4 bytes, assume it was
 		 * including 'status'.
 		 */
-		if (out_field[1] - 8 == remainder)
+		if (out_field[1] - 4 == remainder)
 			return remainder;
-		return out_field[1] - 4;
+		return out_field[1] - 8;
 	} else if (cmd == ND_CMD_CALL) {
 		struct nd_cmd_pkg *pkg = (struct nd_cmd_pkg *) in_field;
 
