On Wed, Jul 18, 2012 at 07:40:32AM +0900, Simon Horman wrote:
> On Tue, Jul 17, 2012 at 11:23:00AM -0400, Vivek Goyal wrote:
> > scan_vmcoreinfo() currently assumes that every line in vmcoreinfo note ends
> > with \n and overwrites new line character 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.
>
> Good plan.
>
> > Signed-off-by: Vivek Goyal <vgoyal at redhat.com>
> > ---
> > vmcore-dmesg/vmcore-dmesg.c | 27 ++++++++++++++++++++++++++-
> > 1 file changed, 26 insertions(+), 1 deletion(-)
> >
> > Index: kexec-tools/vmcore-dmesg/vmcore-dmesg.c
> > ===================================================================
> > --- kexec-tools.orig/vmcore-dmesg/vmcore-dmesg.c 2012-07-19 01:54:02.700700235 -0400
> > +++ kexec-tools/vmcore-dmesg/vmcore-dmesg.c 2012-07-19 01:55:08.232702248 -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;
>
> 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.
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;
}
}
