CVS commit: src/sys/dev/acpi

Module Name:	src
Committed By:	riastradh
Date:		Sun Jul  5 01:51:58 UTC 2026

Modified Files:
	src/sys/dev/acpi: acpi_mcfg.c

Log Message:
acpi(4): Reset mcfg_nsegs to zero if we couldn't find any valid ones.

acpimcfg_probe initializes mcfg_nsegs to the number of segments in
thef MCFG table, and allocates space at mcfg_segs for an array of
segments, but leaves the array zero-initialized.

Later, acpimcfg_init initializes the array with the valid segments,
and _if there are any_, sets mcfg_nsegs to the number of valid ones.

But _if there aren't any_, acpimcfg_init would leave mcfg_nsegs set
to the amount of space allocated in the array, all zero-initialized.

Later still, if PCI_RESOURCE is enabled, acpimcfg_configure_bus
would, via acpimcfg_get_segment, search mcfg_segs[0..mcfg_nsegs) for
an entry matching a PCI segment and bus number, and if they both
happened to be zero, the first one would match...and
acpimcfg_configure_bus would fish the (null!)  seg->ms_bst out of the
all-zero entry and feed it to bus_space_map which would proceed to
barf on the null pointer.

To avoid this, we simply have acpimcfg_init reset mcfg_nsegs to zero
if there are no valid segments found (and free the array, because we
have no further use for it).

This doesn't explain why none of the segments were found to be valid
-- perhaps there's a bug in or around acpi_mcfg.c, or perhaps the
motherboard firmware on the affected hardware is wrong -- but it
should make the failure mode a little more graceful like it was
before without PCI_RESOURCE.

PR kern/60411: x86 PCI_RESOURCE: null pointer dereference at boot


To generate a diff of this commit:
cvs rdiff -u -r1.32 -r1.33 src/sys/dev/acpi/acpi_mcfg.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.