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[RFA] Avoid calling stat with empty name in relocate_gdb_directory
- From: "Pierre Muller" <pierre dot muller at ics-cnrs dot unistra dot fr>
- To: <gdb-patches at sourceware dot org>
- Date: Wed, 5 Dec 2012 18:01:59 +0100
- Subject: [RFA] Avoid calling stat with empty name in relocate_gdb_directory
With the troubles that I have with my patch,
I started looking into a memory debugger...
I finally started to use drmemory
for mingw compiled GDB executables.
This tool reports
Error #1: UNADDRESSABLE ACCESS: reading 0x01fb3a21-0x01fb3a22 1 byte(s)
# 0 msvcrt.dll!_stat32
# 1 relocate_gdb_directory [../../puresrc/gdb/main.c:129]
# 2 captured_main [../../puresrc/gdb/main.c:391]
# 3 catch_errors
[../../puresrc/gdb/exceptions.c:546]
# 4 gdb_main [../../puresrc/gdb/main.c:1041]
# 5 main [../../puresrc/gdb/gdb.c:34]
Note: @0:00:00.733 in thread 6596
Note: refers to 1 byte(s) beyond last valid byte in prior malloc
Note: prev lower malloc: 0x01fb3a20-0x01fb3a21
Note: instruction: cmp 0x01(%edi) $0x3a
line 129 of main.c is:
if (stat (dir, &s) != 0 || !S_ISDIR (s.st_mode))
The unauthorized access is due to a call to stat function with dir = ""
it seems that dir[1] is access despite the fact that (dir[0]=='\0')
I don't know if stat is supposed to handle (*dir == '\0'),
but I thought that it should anyhow succeed in that case,
so the patch below simply don't call stat if name is empty.
Tell me if you rather think that this is a msvcrt bug that
should not be fixed in GDB...
Pierre Muller
GDB pascal language maintainer
2012-12-05 Pierre Muller <muller@sourceware.org>
* main.c (relocate_gdb_directory): Avoid calling stat function
if DIR is empty.
Index: src/gdb/main.c
===================================================================
RCS file: /cvs/src/src/gdb/main.c,v
retrieving revision 1.115
diff -u -p -r1.115 main.c
--- src/gdb/main.c 16 Nov 2012 19:43:38 -0000 1.115
+++ src/gdb/main.c 5 Dec 2012 16:54:40 -0000
@@ -126,7 +126,7 @@ relocate_gdb_directory (const char *init
{
struct stat s;
- if (stat (dir, &s) != 0 || !S_ISDIR (s.st_mode))
+ if (*dir == '\0' || stat (dir, &s) != 0 || !S_ISDIR (s.st_mode))
{
xfree (dir);
dir = NULL;
~