64 lines
2.2 KiB
Diff
64 lines
2.2 KiB
Diff
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From c0e295af1adca6a0258bb405c535fe04969cc178 Mon Sep 17 00:00:00 2001
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From: Olivier Fourdan <ofourdan@redhat.com>
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Date: Wed, 27 Nov 2024 14:41:45 +0100
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Subject: [PATCH xserver 03/13] xkb: Fix buffer overflow in XkbVModMaskText()
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The code in XkbVModMaskText() allocates a fixed sized buffer on the
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stack and copies the virtual mod name.
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There's actually two issues in the code that can lead to a buffer
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overflow.
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First, the bound check mixes pointers and integers using misplaced
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parenthesis, defeating the bound check.
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But even though, if the check fails, the data is still copied, so the
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stack overflow will occur regardless.
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Change the logic to skip the copy entirely if the bound check fails.
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CVE-2025-26595, ZDI-CAN-25545
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This vulnerability was discovered by:
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Jan-Niklas Sohn working with Trend Micro Zero Day Initiative
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Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
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Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
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(cherry picked from commit 11fcda8753e994e15eb915d28cf487660ec8e722)
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Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1831>
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---
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xkb/xkbtext.c | 16 ++++++++--------
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1 file changed, 8 insertions(+), 8 deletions(-)
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diff --git a/xkb/xkbtext.c b/xkb/xkbtext.c
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index d2a2567fc..002626450 100644
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--- a/xkb/xkbtext.c
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+++ b/xkb/xkbtext.c
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@@ -175,14 +175,14 @@ XkbVModMaskText(XkbDescPtr xkb,
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len = strlen(tmp) + 1 + (str == buf ? 0 : 1);
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if (format == XkbCFile)
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len += 4;
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- if ((str - (buf + len)) <= VMOD_BUFFER_SIZE) {
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- if (str != buf) {
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- if (format == XkbCFile)
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- *str++ = '|';
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- else
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- *str++ = '+';
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- len--;
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- }
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+ if ((str - buf) + len > VMOD_BUFFER_SIZE)
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+ continue; /* Skip */
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+ if (str != buf) {
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+ if (format == XkbCFile)
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+ *str++ = '|';
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+ else
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+ *str++ = '+';
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+ len--;
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}
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if (format == XkbCFile)
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sprintf(str, "%sMask", tmp);
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--
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2.48.1
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