From 8d3b6f9da468f666e3a7976657f2ab5c52762a21 Mon Sep 17 00:00:00 2001
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From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Date: Tue, 7 Jul 2020 15:12:25 -0400
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Subject: [PATCH] term: Fix overflow on user inputs
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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This requires a very weird input from the serial interface but can cause
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an overflow in input_buf (keys) overwriting the next variable (npending)
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with the user choice:
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(pahole output)
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struct grub_terminfo_input_state {
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int input_buf[6]; /* 0 24 */
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int npending; /* 24 4 */ <- CORRUPT
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...snip...
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The magic string requires causing this is "ESC,O,],0,1,2,q" and we overflow
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npending with "q" (aka increase npending to 161). The simplest fix is to
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just to disallow overwrites input_buf, which exactly what this patch does.
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Fixes: CID 292449
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Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
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Signed-off-by: Stefan Sørensen <stefan.sorensen@spectralink.com>
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---
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grub-core/term/terminfo.c | 9 ++++++---
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1 file changed, 6 insertions(+), 3 deletions(-)
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diff --git a/grub-core/term/terminfo.c b/grub-core/term/terminfo.c
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index d317efa36..5fa94c0c3 100644
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--- a/grub-core/term/terminfo.c
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+++ b/grub-core/term/terminfo.c
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@@ -398,7 +398,7 @@ grub_terminfo_getwh (struct grub_term_output *term)
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}
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static void
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-grub_terminfo_readkey (struct grub_term_input *term, int *keys, int *len,
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+grub_terminfo_readkey (struct grub_term_input *term, int *keys, int *len, int max_len,
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int (*readkey) (struct grub_term_input *term))
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{
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int c;
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@@ -414,6 +414,9 @@ grub_terminfo_readkey (struct grub_term_input *term, int *keys, int *len,
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if (c == -1) \
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return; \
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\
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+ if (*len >= max_len) \
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+ return; \
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+ \
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keys[*len] = c; \
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(*len)++; \
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}
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@@ -602,8 +605,8 @@ grub_terminfo_getkey (struct grub_term_input *termi)
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return ret;
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}
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- grub_terminfo_readkey (termi, data->input_buf,
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- &data->npending, data->readkey);
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+ grub_terminfo_readkey (termi, data->input_buf, &data->npending,
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+ GRUB_TERMINFO_READKEY_MAX_LEN, data->readkey);
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#if defined(__powerpc__) && defined(GRUB_MACHINE_IEEE1275)
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if (data->npending == 1 && data->input_buf[0] == GRUB_TERM_ESC
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--
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2.26.2
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