PCI/sysfs: Fix dsm_label_utf16s_to_utf8s() buffer overrun

[ Upstream commit bdcdaa13ad96f1a530711c29e6d4b8311eff767c ]

"utf16s_to_utf8s(..., buf, PAGE_SIZE)" puts up to PAGE_SIZE bytes into
"buf" and returns the number of bytes it actually put there.  If it wrote
PAGE_SIZE bytes, the newline added by dsm_label_utf16s_to_utf8s() would
overrun "buf".

Reduce the size available for utf16s_to_utf8s() to use so there is always
space for the newline.

[bhelgaas: reorder patch in series, commit log]
Fixes: 6058989bad05 ("PCI: Export ACPI _DSM provided firmware instance number and string name to sysfs")
Link: https://lore.kernel.org/r/20210603000112.703037-7-kw@linux.com
Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Krzysztof Wilczyński <kw@linux.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/pci/pci-label.c b/drivers/pci/pci-label.c
index a961a71d950fb604133f0f877ab60cce7aff110b..6beafc1bee96a162a5b07d0e7c45e86dc596065a 100644 (file)
--- a/drivers/pci/pci-label.c
+++ b/drivers/pci/pci-label.c
@@ -161,7 +161,7 @@ static void dsm_label_utf16s_to_utf8s(union acpi_object *obj, char *buf)
        len = utf16s_to_utf8s((const wchar_t *)obj->buffer.pointer,
                              obj->buffer.length,
                              UTF16_LITTLE_ENDIAN,
-                             buf, PAGE_SIZE);
+                             buf, PAGE_SIZE - 1);
        buf[len] = '\n';
 }