On Wed, Jul 18, 2012 at 09:33:51AM -0400, Vivek Goyal wrote:
[..]
> > > + char temp_buf[1024];
> > > + bool last_line = false;
> >
> > Is there a chance of over-running temp_buf?
> >
> > I would be more comfortable if there was a check below to
> > ensure that len can never be greater than sizeof(temp_buf).
>
> Hi Simon,
>
> Agreed. Making sure temp_buf does not overflow is a good idea. Here is
> the udpated patch.
>
Hi Simon,
Do you have any more concerns with this patch. If not, can you please
apply it.
Thanks
Vivek
> Thanks
> Vivek
>
>
> vmcore-dmesg: Do not write beyond end of buffer
>
> scan_vmcoreinfo() currently assumes that every vmcoreinfo note line ends
> with \n and overwrites new line with \0. But last entry in note, CRASHTIME=
> does not end with \n and this leads to corrupting memory as we write beyond
> end of buffer.
>
> Normally things were fine but when I added some fields to vmcoreinfo, this
> bug started showing and vmcore-dmesg started crashing.
>
> I am planning to send a patch to fix this in kernel but it might be good
> idea to handle this case in user space too so that vmcore-dmesg works
> fine with cores of older kernels.
>
> Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
> ---
> vmcore-dmesg/vmcore-dmesg.c | 29 ++++++++++++++++++++++++++++-
> 1 file changed, 28 insertions(+), 1 deletion(-)
>
> Index: kexec-tools/vmcore-dmesg/vmcore-dmesg.c
> ===================================================================
> --- kexec-tools.orig/vmcore-dmesg/vmcore-dmesg.c 2012-07-20 08:04:42.370051049 -0400
> +++ kexec-tools/vmcore-dmesg/vmcore-dmesg.c 2012-07-20 08:12:14.198070252 -0400
> @@ -14,6 +14,7 @@
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <elf.h>
> +#include <stdbool.h>
>
> /* The 32bit and 64bit note headers make it clear we don't care */
> typedef Elf32_Nhdr Elf_Nhdr;
> @@ -220,6 +221,9 @@ static void scan_vmcoreinfo(char *start,
> {
> char *last = start + size - 1;
> char *pos, *eol;
> + char temp_buf[1024];
> + bool last_line = false;
> +
> #define SYMBOL(sym) { \
> .str = "SYMBOL(" #sym ")=", \
> .name = #sym, \
> @@ -243,7 +247,27 @@ static void scan_vmcoreinfo(char *start,
> /* Find the end of the current line */
> for (eol = pos; (eol <= last) && (*eol != '\n') ; eol++)
> ;
> - len = eol - pos + 1;
> + if (eol > last) {
> + /*
> + * We did not find \n and note ended. Currently kernel
> + * is appending last field CRASH_TIME without \n. It
> + * is ugly but handle it.
> + */
> + eol = last;
> + len = eol - pos + 1;
> + if (len >= sizeof(temp_buf))
> + len = sizeof(temp_buf) - 1;
> + strncpy(temp_buf, pos, len);
> + temp_buf[len + 1] = '\0';
> +
> + pos = temp_buf;
> + len = len + 1;
> + eol = pos + len -1;
> + last_line = true;
> + } else {
> + len = eol - pos + 1;
> + }
> +
> /* Stomp the last character so I am guaranteed a terminating null */
> *eol = '\0';
> /* Copy OSRELEASE if I see it */
> @@ -266,6 +290,9 @@ static void scan_vmcoreinfo(char *start,
> /* Remember the virtual address */
> *symbol[i].vaddr = vaddr;
> }
> +
> + if (last_line)
> + break;
> }
> }
>
>
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