[coreboot-gerrit] Change in coreboot[master]: spi/flashconsole: Fix internal buffer overflow

[Nico Huber (Code Review)]

Nico Huber has submitted this change. ( https://review.coreboot.org/c/coreboot/+/48074 )

Change subject: spi/flashconsole: Fix internal buffer overflow
......................................................................

spi/flashconsole: Fix internal buffer overflow

Once the console's FMAP region is full, we stop clearing the line
buffer and `line_offset` is not reset anymore. Hence, sanity check
`line_offset` everytime before writing to the buffer.

The issue resulted in boot hangs and potentially a brick if the
log was very verbose.

Change-Id: I36e9037d7baf8c1ed8b2d0c120bfffa58c089c95
Signed-off-by: Nico Huber 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48074
Reviewed-by: Paul Menzel 
Reviewed-by: Michael Niewöhner 
Reviewed-by: Angel Pons 
Tested-by: build bot (Jenkins) 
---
M src/drivers/spi/flashconsole.c
1 file changed, 2 insertions(+), 1 deletion(-)

Approvals:
  build bot (Jenkins): Verified
  Paul Menzel: Looks good to me, but someone else must approve
  Angel Pons: Looks good to me, but someone else must approve
  Michael Niewöhner: Looks good to me, approved

diff --git a/src/drivers/spi/flashconsole.c b/src/drivers/spi/flashconsole.c
index 654177f..d5c4382 100644
--- a/src/drivers/spi/flashconsole.c
+++ b/src/drivers/spi/flashconsole.c
@@ -75,7 +75,8 @@

size_t region_size = region_device_sz(rdev_ptr);

-	line_buffer[line_offset++] = c;
+	if (line_offset < LINE_BUFFER_SIZE)
+		line_buffer[line_offset++] = c;

if (line_offset >= LINE_BUFFER_SIZE ||
        offset + line_offset >= region_size || c == '\n') {