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From ad3a19e6372b1e667128ed1ea2f49919884587e1 Mon Sep 17 00:00:00 2001
From: Akira TAGOH <akira@tagoh.org>
Date: Thu, 17 Feb 2022 17:30:12 +0900
Subject: [PATCH] Fix the stack buffer overflow issue
strlen() could returns 0. Without a conditional check for len,
accessing S_ pointer with len - 1 may causes a stack buffer overflow.
AddressSanitizer reports this like:
==1219243==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffdce043c1f at pc 0x000000403547 bp 0x7ffdce0
43b30 sp 0x7ffdce043b28
READ of size 1 at 0x7ffdce043c1f thread T0
#0 0x403546 in main ../bin/fribidi-main.c:393
#1 0x7f226804e58f in __libc_start_call_main (/lib64/libc.so.6+0x2d58f)
#2 0x7f226804e648 in __libc_start_main_impl (/lib64/libc.so.6+0x2d648)
#3 0x4036f4 in _start (/tmp/fribidi/build/bin/fribidi+0x4036f4)
Address 0x7ffdce043c1f is located in stack of thread T0 at offset 63 in frame
#0 0x4022bf in main ../bin/fribidi-main.c:193
This frame has 5 object(s):
[32, 36) 'option_index' (line 233)
[48, 52) 'base' (line 386)
[64, 65064) 'S_' (line 375) <== Memory access at offset 63 underflows this variable
[65328, 130328) 'outstring' (line 385)
[130592, 390592) 'logical' (line 384)
This fixes https://github.com/fribidi/fribidi/issues/181
---
bin/fribidi-main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/bin/fribidi-main.c b/bin/fribidi-main.c
index 3cf9fe1..3ae4fb6 100644
--- a/bin/fribidi-main.c
+++ b/bin/fribidi-main.c
@@ -390,7 +390,7 @@ FRIBIDI_END_IGNORE_DEPRECATIONS
S_[sizeof (S_) - 1] = 0;
len = strlen (S_);
/* chop */
- if (S_[len - 1] == '\n')
+ if (len > 0 && S_[len - 1] == '\n')
{
len--;
S_[len] = '\0';
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