On 08/09/11 10:06, Andrew Morton wrote:
On Thu, 08 Sep 2011 09:54:18 +1000
Ryan Mallon<rmallon@xxxxxxxxx> wrote:
strnlen_user returns the length of the string including the nul
terminator. In the case where maxlen is reached strnlen_user returns
maxlen + 1. Most callsites already check for this condition. Fix the
call to strnlen_user in fs/exec.c to check for the maxlen case.
diff --git a/fs/exec.c b/fs/exec.c
index 25dcbe5..e19588c 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -481,7 +481,7 @@ static int copy_strings(int argc, struct
user_arg_ptr argv,
goto out;
len = strnlen_user(str, MAX_ARG_STRLEN);
- if (!len)
+ if (!len || len> MAX_ARG_STRLEN)
goto out;
ret = -E2BIG;
The following call to vald_arg_len() already does this?
This change will cause copy_strings() to incorrectly return -EFAULT,
rather than -E2BIG.
Hmm, missed that. How about the patch below instead which passes the
correct length to strnlen_user?
Your email client is wordwrapping and space-stuffing the patches, btw.
I'll try again. Hopefully it works this time.
---
Replace valid_arg_len function in fs/exec.c with max_arg_len function
and pass the correct length to strnlen_user.
Signed-off-by: Ryan Mallon <rmallon@xxxxxxxxx>
---
diff --git a/fs/exec.c b/fs/exec.c
index e19588c..12d2f7f 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -296,9 +296,9 @@ err:
return err;
}
-static bool valid_arg_len(struct linux_binprm *bprm, long len)
+static long max_arg_len(struct linux_binprm *bprm)
{
- return len<= MAX_ARG_STRLEN;
+ return MAX_ARG_STRLEN;
}
#else
@@ -354,9 +354,9 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
return 0;
}
-static bool valid_arg_len(struct linux_binprm *bprm, long len)
+static long max_arg_len(struct linux_binprm *bprm)
{
- return len<= bprm->p;
+ return bprm->p;
}
#endif /* CONFIG_MMU */
@@ -474,18 +474,19 @@ static int copy_strings(int argc, struct user_arg_ptr argv,
const char __user *str;
int len;
unsigned long pos;
+ long max_len = max_arg_len(bprm);
ret = -EFAULT;
str = get_user_arg_ptr(argv, argc);
if (IS_ERR(str))
goto out;
- len = strnlen_user(str, MAX_ARG_STRLEN);
- if (!len || len> MAX_ARG_STRLEN)
+ len = strnlen_user(str, max_len);
+ if (!len)
goto out;
ret = -E2BIG;
- if (!valid_arg_len(bprm, len))
+ if (len> max_len)
goto out;
/* We're going to work our way backwords. */
--
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