From ad3a19e6372b1e667128ed1ea2f49919884587e1 Mon Sep 17 00:00:00 2001 From: Akira TAGOH 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';