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[109.252.90.50]) by smtp.gmail.com with ESMTPSA id mt4sm894626lbc.31.2016.04.08.21.01.51 for (version=TLSv1/SSLv3 cipher=OTHER); Fri, 08 Apr 2016 21:01:51 -0700 (PDT) Subject: Re: [PATCH] grub-file: fix segmentation fault To: grub-devel@gnu.org References: <20160408064322.GA15761@linux-9gqx.suse> From: Andrei Borzenkov X-Enigmail-Draft-Status: N1110 Message-ID: <57087EAE.6070903@gmail.com> Date: Sat, 9 Apr 2016 07:01:50 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20160408064322.GA15761@linux-9gqx.suse> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2a00:1450:4010:c07::22d X-BeenThere: grub-devel@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: The development of GNU GRUB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 09 Apr 2016 04:01:59 -0000 08.04.2016 09:43, Michael Chang пишет: > In grub_file_open the file handle returned by file filters has no file->name > set which leads to segmentation fault later referenced by grub_elf_file. We > move the file->name value assignment after file filters to make sure it will be > set and returned. > This now makes filename unavailable to progress module (which gets the last grub_file in a chain) and it still does not cover corner case of failing grub_strdup in grub_file_open. Fixing the former requires some redesign. But as long as we allow filename to remain empty in grub_file_open every user must explicitly check for it being NULL. > The stack backtrace for reference. > > gdb --args ./grub-file --is-x86_64-xen-domu /boot/vmlinux-4.1.12-1-default.gz > > (gdb) bt > #0 0x000000000047597e in grub_strlen (s=0x0) at ../grub-core/kern/misc.c:558 > #1 0x00000000004757e2 in grub_strdup (s=0x0) at ../grub-core/kern/misc.c:463 > #2 0x0000000000406418 in grub_elf_file (file=0x6dfb50, filename=0x0) at ../grub-core/kern/elf.c:89 > #3 0x00000000004043b3 in grub_xen_file (file=0x6dfb50) at ../grub-core/loader/i386/xen_file.c:29 > #4 0x0000000000403930 in grub_cmd_file (ctxt=0x7fffffffe120, argc=1, args=0x6dfa00) at ../grub-core/commands/file.c:425 > #5 0x000000000047e178 in grub_extcmd_dispatcher (cmd=0x6df730, argc=2, args=0x6ddfb0, script=0x0) at ../grub-core/commands/extcmd.c:54 > #6 0x000000000047e1d7 in grub_extcmd_dispatch (cmd=0x6df730, argc=2, args=0x6ddfb0) at ../grub-core/commands/extcmd.c:67 > #7 0x0000000000402945 in main (argc=3, argv=0x7fffffffe2e8) at ../util/grub-file.c:102 > (gdb) frame 3 > #3 0x00000000004043b3 in grub_xen_file (file=0x6dfb50) at ../grub-core/loader/i386/xen_file.c:29 > 29 elf = grub_elf_file (file, file->name); > --- > grub-core/kern/file.c | 10 ++++++---- > 1 file changed, 6 insertions(+), 4 deletions(-) > > diff --git a/grub-core/kern/file.c b/grub-core/kern/file.c > index 668f893..44047d7 100644 > --- a/grub-core/kern/file.c > +++ b/grub-core/kern/file.c > @@ -111,9 +111,6 @@ grub_file_open (const char *name) > if ((file->fs->open) (file, file_name) != GRUB_ERR_NONE) > goto fail; > > - file->name = grub_strdup (name); > - grub_errno = GRUB_ERR_NONE; > - > for (filter = 0; file && filter < ARRAY_SIZE (grub_file_filters_enabled); > filter++) > if (grub_file_filters_enabled[filter]) > @@ -123,7 +120,12 @@ grub_file_open (const char *name) > } > if (!file) > grub_file_close (last_file); > - > + else > + { > + file->name = grub_strdup (name); > + grub_errno = GRUB_ERR_NONE; > + } > + > grub_memcpy (grub_file_filters_enabled, grub_file_filters_all, > sizeof (grub_file_filters_enabled)); > >