[PATCH] realpath: Do not copy result on failure (BZ #28815)

[PATCH] realpath: Do not copy result on failure (BZ #28815)

[Siddhesh Poyarekar]

On failure, the contents of the resolved buffer passed in by the caller
to realpath are undefined.  Do not copy any partial resolution to the
buffer and also do not test resolved contents in test-canon.c.

Resolves: BZ #28815

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
 stdlib/canonicalize.c | 4 ++--
 stdlib/test-canon.c   | 4 +++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
index 6caed9e70e..6237a41d42 100644
--- a/stdlib/canonicalize.c
+++ b/stdlib/canonicalize.c
@@ -400,11 +400,11 @@ realpath_stk (const char *name, char *resolved,
 
 error:
   *dest++ = '\0';
-  if (resolved != NULL)
+  if (!failed && resolved != NULL)
     {
       if (dest - rname <= get_path_max ())
 	rname = strcpy (resolved, rname);
-      else if (!failed)
+      else
 	{
 	  failed = true;
 	  __set_errno (ENAMETOOLONG);
diff --git a/stdlib/test-canon.c b/stdlib/test-canon.c
index 185ccf4f48..2ad1218749 100644
--- a/stdlib/test-canon.c
+++ b/stdlib/test-canon.c
@@ -174,7 +174,9 @@ do_test (int argc, char ** argv)
 	  continue;
 	}
 
-      if (!check_path (buf, tests[i].out ? tests[i].out : tests[i].resolved))
+      /* Only on success verify that buf contains the result too.  */
+      if (result != NULL
+	  && !check_path (buf, tests[i].out ? tests[i].out : tests[i].resolved))
 	{
 	  printf ("%s: flunked test %d (expected resolved `%s', got `%s')\n",
 		  argv[0], i, tests[i].out ? tests[i].out : tests[i].resolved,
-- 
2.34.1

Re: [PATCH] realpath: Do not copy result on failure (BZ #28815)

[Adhemerval Zanella]

On 24/01/2022 13:54, Siddhesh Poyarekar via Libc-alpha wrote:
> On failure, the contents of the resolved buffer passed in by the caller
> to realpath are undefined.  Do not copy any partial resolution to the
> buffer and also do not test resolved contents in test-canon.c.
> 
> Resolves: BZ #28815
> 
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  stdlib/canonicalize.c | 4 ++--
>  stdlib/test-canon.c   | 4 +++-
>  2 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
> index 6caed9e70e..6237a41d42 100644
> --- a/stdlib/canonicalize.c
> +++ b/stdlib/canonicalize.c
> @@ -400,11 +400,11 @@ realpath_stk (const char *name, char *resolved,
>  
>  error:
>    *dest++ = '\0';
> -  if (resolved != NULL)
> +  if (!failed && resolved != NULL)
>      {
>        if (dest - rname <= get_path_max ())
>  	rname = strcpy (resolved, rname);
> -      else if (!failed)
> +      else
>  	{
>  	  failed = true;
>  	  __set_errno (ENAMETOOLONG);
> diff --git a/stdlib/test-canon.c b/stdlib/test-canon.c
> index 185ccf4f48..2ad1218749 100644
> --- a/stdlib/test-canon.c
> +++ b/stdlib/test-canon.c
> @@ -174,7 +174,9 @@ do_test (int argc, char ** argv)
>  	  continue;
>  	}
>  
> -      if (!check_path (buf, tests[i].out ? tests[i].out : tests[i].resolved))
> +      /* Only on success verify that buf contains the result too.  */
> +      if (result != NULL
> +	  && !check_path (buf, tests[i].out ? tests[i].out : tests[i].resolved))
>  	{
>  	  printf ("%s: flunked test %d (expected resolved `%s', got `%s')\n",
>  		  argv[0], i, tests[i].out ? tests[i].out : tests[i].resolved,