From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Tue, 7 Jul 2020 15:12:25 -0400
Subject: [PATCH] term: Fix overflow on user inputs
This requires a very weird input from the serial interface but can cause
an overflow in input_buf (keys) overwriting the next variable (npending)
with the user choice:
(pahole output)
struct grub_terminfo_input_state {
int input_buf[6]; /* 0 24 */
int npending; /* 24 4 */ <- CORRUPT
...snip...
The magic string requires causing this is "ESC,O,],0,1,2,q" and we overflow
npending with "q" (aka increase npending to 161). The simplest fix is to
just to disallow overwrites input_buf, which exactly what this patch does.
Fixes: CID 292449
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Upstream-commit-id: 98dfa546777
---
grub-core/term/terminfo.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/grub-core/term/terminfo.c b/grub-core/term/terminfo.c
index 537a5c0cb0b..44d0b3b19fb 100644
--- a/grub-core/term/terminfo.c
+++ b/grub-core/term/terminfo.c
@@ -398,7 +398,7 @@ grub_terminfo_getwh (struct grub_term_output *term)
}
static void
-grub_terminfo_readkey (struct grub_term_input *term, int *keys, int *len,
+grub_terminfo_readkey (struct grub_term_input *term, int *keys, int *len, int max_len,
int (*readkey) (struct grub_term_input *term))
{
int c;
@@ -414,6 +414,9 @@ grub_terminfo_readkey (struct grub_term_input *term, int *keys, int *len,
if (c == -1) \
return; \
\
+ if (*len >= max_len) \
+ return; \
+ \
keys[*len] = c; \
(*len)++; \
}
@@ -602,8 +605,8 @@ grub_terminfo_getkey (struct grub_term_input *termi)
return ret;
}
- grub_terminfo_readkey (termi, data->input_buf,
- &data->npending, data->readkey);
+ grub_terminfo_readkey (termi, data->input_buf, &data->npending,
+ GRUB_TERMINFO_READKEY_MAX_LEN, data->readkey);
#if defined(__powerpc__) && defined(GRUB_MACHINE_IEEE1275)
if (data->npending == 1 && data->input_buf[0] == GRUB_TERM_ESC