Artem Frolov wrote:
Hello,
I am in the process of testing static defect analyzer on a Linux
kernel source code (see disclosure below).
I found some potential array bounds violations. The pattern is as
follows: bytes are copied from the user space and then buffer is
accessed on index strlen(buf)-1. This is a defect if user data start
from 0. So the question is: can we make any assumptions what data may
be received from the user or it could be arbitrary?
Both are potential problems for someone with CAP_SYS_ADMIN
capabilties. Attached are patches for them.
Full disclosure: I am working for Klocwork (http://www.klocwork.com/),
which is a vendor of commercial closed-source proprietary products,
static analyzer for C/C++ is part of its products
--
~Randy
mtrr: prevent copy_from_user(to, from, -1) or (if that should
succeed somehow) write to line[-1] (on stack);
Signed-off-by: Randy Dunlap <[EMAIL PROTECTED]>
diffstat:=
arch/i386/kernel/cpu/mtrr/if.c | 8 ++++++--
1 files changed, 6 insertions(+), 2 deletions(-)
diff -Naurp ./arch/i386/kernel/cpu/mtrr/if.c~mtrr_strlen ./arch/i386/kernel/cpu/mtrr/if.c
--- ./arch/i386/kernel/cpu/mtrr/if.c~mtrr_strlen 2005-03-01 23:37:50.000000000 -0800
+++ ./arch/i386/kernel/cpu/mtrr/if.c 2005-03-15 20:02:35.000000000 -0800
@@ -98,16 +98,20 @@ mtrr_write(struct file *file, const char
unsigned long long base, size;
char *ptr;
char line[LINE_SIZE];
+ size_t linelen;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
+ if (!len)
+ return -EINVAL;
memset(line, 0, LINE_SIZE);
if (len > LINE_SIZE)
len = LINE_SIZE;
if (copy_from_user(line, buf, len - 1))
return -EFAULT;
- ptr = line + strlen(line) - 1;
- if (*ptr == '\n')
+ linelen = strlen(line);
+ ptr = line + linelen - 1;
+ if (linelen && *ptr == '\n')
*ptr = '\0';
if (!strncmp(line, "disable=", 8)) {
reg = simple_strtoul(line + 8, &ptr, 0);
cciss: prevent write to cmd[-1] (on stack);
Signed-off-by: Randy Dunlap <[EMAIL PROTECTED]>
diffstat:=
drivers/block/cciss.c | 2 +-
1 files changed, 1 insertion(+), 1 deletion(-)
diff -Naurp ./drivers/block/cciss.c~cciss_strlen ./drivers/block/cciss.c
--- ./drivers/block/cciss.c~cciss_strlen 2005-03-14 15:28:18.000000000 -0800
+++ ./drivers/block/cciss.c 2005-03-15 14:53:52.000000000 -0800
@@ -304,7 +304,7 @@ cciss_proc_write(struct file *file, cons
if (copy_from_user(cmd, buffer, count)) return -EFAULT;
cmd[count] = '\0';
len = strlen(cmd); // above 3 lines ensure safety
- if (cmd[len-1] == '\n')
+ if (len && cmd[len-1] == '\n')
cmd[--len] = '\0';
# ifdef CONFIG_CISS_SCSI_TAPE
if (strcmp("engage scsi", cmd)==0) {
