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From: Andrey Konovalov <andreyknvl@google.com>
To: Dave Jones <davej@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Andrey Konovalov <andreyknvl@google.com>,
	linux-kernel@vger.kernel.org, fweisbec@gmail.com,
	mingo@redhat.com, Dmitry Vyukov <dvyukov@google.com>,
	Kostya Serebryany <kcc@google.com>
Subject: Re: Fwd: Potential out-of-bounds in ftrace_regex_release
Date: Wed, 9 Oct 2013 14:05:26 +0400	[thread overview]
Message-ID: <CAAeHK+wTs3THbh+EVoTm0wqQH8cg2VbT8aKYBX67A385+ohq0w@mail.gmail.com> (raw)
In-Reply-To: <20131002223437.GA15728@redhat.com>

I got one more report of a similar bug:

AddressSanitizer: heap-buffer-overflow on address ffff8800205f0e40
Write of size 1 by thread T14005:
 [<ffffffff811e2542>] ftrace_event_write+0xe2/0x130
./kernel/trace/trace_events.c:583
 [<ffffffff8128c497>] vfs_write+0x127/0x2f0 ??:0
 [<ffffffff8128d572>] SyS_write+0x72/0xd0 ??:0
 [<ffffffff818423d2>] system_call_fastpath+0x16/0x1b
./arch/x86/kernel/entry_64.S:629

Allocated by thread T14005:
 [<     inlined    >] trace_parser_get_init+0x28/0x70 kmalloc
./include/linux/slab.h:413
 [<ffffffff811cc258>] trace_parser_get_init+0x28/0x70 ./kernel/trace/trace.c:759
 [<ffffffff811e24d2>] ftrace_event_write+0x72/0x130
./kernel/trace/trace_events.c:572
 [<ffffffff8128c497>] vfs_write+0x127/0x2f0 ??:0
 [<ffffffff8128d572>] SyS_write+0x72/0xd0 ??:0
 [<ffffffff818423d2>] system_call_fastpath+0x16/0x1b
./arch/x86/kernel/entry_64.S:629

The buggy address ffff8800205f0e40 is located 0 bytes to the right
 of 128-byte region [ffff8800205f0dc0, ffff8800205f0e40)

Memory state around the buggy address:
 ffff8800205f0900: rrrrrrrr rrrrrrrr rrrrrrrr rrrrrrrr
 ffff8800205f0a00: rrrrrrrr ........ ........ rrrrrrrr
 ffff8800205f0b00: rrrrrrrr rrrrrrrr rrrrrrrr rrrrrrrr
 ffff8800205f0c00: ........ .......5 rrrrrrrr rrrrrrrr
 ffff8800205f0d00: rrrrrrrr rrrrrrrr rrrrrrrr ........
>ffff8800205f0e00: ........ rrrrrrrr rrrrrrrr rrrrrrrr
                            ^
 ffff8800205f0f00: rrrrrrrr rrrrrrrr rrrrrrrr rrrrrrrr
 ffff8800205f1000: ........ ........ ........ ........
 ffff8800205f1100: ........ ........ ........ ........
 ffff8800205f1200: ........ ........ ........ ........
 ffff8800205f1300: ........ ........ ........ ........
Legend:
 f - 8 freed bytes
 r - 8 redzone bytes
 . - 8 allocated bytes
 x=1..7 - x allocated bytes + (8-x) redzone bytes

This time it was caused by 'parser.buffer[parser.idx] = 0;' in
'ftrace_event_write()', which calls 'trace_get_user()' right before
the bad assignment.

So I still think that the bug is in 'trage_get_user()':
Checking that 'parser->idx < parser->size - 1' is not performed in 'if
(isspace(ch))' section, so 'parser->idx' becomes equal to
'parser->size' after 'parser->buffer[parser->idx++] = ch;'.
(However in 'while (cnt && !isspace(ch))' loop checking is performed.)

  reply	other threads:[~2013-10-09 10:05 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CAAeHK+w+8=DGvFeuMAwS50RRvAGw1KkWHcivja5q-wmX8GtH2w@mail.gmail.com>
2013-10-02 18:38 ` Fwd: Potential out-of-bounds in ftrace_regex_release Andrey Konovalov
2013-10-02 18:57   ` Dave Jones
2013-10-02 19:06     ` Andrey Konovalov
2013-10-02 20:18     ` Steven Rostedt
2013-10-02 22:34       ` Dave Jones
2013-10-09 10:05         ` Andrey Konovalov [this message]
2013-10-10  2:23           ` Steven Rostedt
2013-10-14  8:29             ` Andrey Konovalov
2013-10-18 19:09               ` Steven Rostedt
2013-10-21  7:33                 ` Andrey Konovalov

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