diff mbox series

[hurd,commited] hurd: Fix readlink() hanging on fifo

Message ID 20220914165827.118893-1-samuel.thibault@ens-lyon.org
State New
Headers show
Series [hurd,commited] hurd: Fix readlink() hanging on fifo | expand

Commit Message

Samuel Thibault Sept. 14, 2022, 4:58 p.m. UTC 
readlink() opens the target with O_READ to be able to read the symlink
content. When the target is actually a fifo, that would hang waiting for a
writer (caught in the coreutils testsuite). We thus have to first lookup the
target without O_READ to perform io_stat and lookout for fifos, and only
after checking the symlink type, we can re-lookup with O_READ.
---
 sysdeps/mach/hurd/readlink.c   | 5 ++++-
 sysdeps/mach/hurd/readlinkat.c | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

Comments

Andreas Schwab Sept. 14, 2022, 5:04 p.m. UTC | #1 
On Sep 14 2022, Samuel Thibault wrote:

> diff --git a/sysdeps/mach/hurd/readlink.c b/sysdeps/mach/hurd/readlink.c
> index 770462714f..2d75ef7725 100644
> --- a/sysdeps/mach/hurd/readlink.c
> +++ b/sysdeps/mach/hurd/readlink.c
> @@ -31,7 +31,7 @@ __readlink (const char *file_name, char *buf, size_t len)
>    file_t file;
>    struct stat64 st;
>  
> -  file = __file_name_lookup (file_name, O_READ | O_NOLINK, 0);
> +  file = __file_name_lookup (file_name, O_NOLINK, 0);
>    if (file == MACH_PORT_NULL)
>      return -1;
>  
> @@ -41,6 +41,9 @@ __readlink (const char *file_name, char *buf, size_t len)
>        {
>  	char *rbuf = buf;
>  
> +	__mach_port_deallocate (__mach_task_self (), file);
> +	file = __file_name_lookup (file_name, O_READ | O_NOLINK, 0);

How do you know that file_name still points at the same thing?
Samuel Thibault Sept. 15, 2022, 7:56 p.m. UTC | #2 
Andreas Schwab, le mer. 14 sept. 2022 19:04:52 +0200, a ecrit:
> On Sep 14 2022, Samuel Thibault wrote:
> > diff --git a/sysdeps/mach/hurd/readlink.c b/sysdeps/mach/hurd/readlink.c
> > index 770462714f..2d75ef7725 100644
> > --- a/sysdeps/mach/hurd/readlink.c
> > +++ b/sysdeps/mach/hurd/readlink.c
> > @@ -31,7 +31,7 @@ __readlink (const char *file_name, char *buf, size_t len)
> >    file_t file;
> >    struct stat64 st;
> >  
> > -  file = __file_name_lookup (file_name, O_READ | O_NOLINK, 0);
> > +  file = __file_name_lookup (file_name, O_NOLINK, 0);
> >    if (file == MACH_PORT_NULL)
> >      return -1;
> >  
> > @@ -41,6 +41,9 @@ __readlink (const char *file_name, char *buf, size_t len)
> >        {
> >  	char *rbuf = buf;
> >  
> > +	__mach_port_deallocate (__mach_task_self (), file);
> > +	file = __file_name_lookup (file_name, O_READ | O_NOLINK, 0);
> 
> How do you know that file_name still points at the same thing?

Righ, better make that atomic. I have pushed it so.

Thanks,
Samuel
diff mbox series

Patch

diff --git a/sysdeps/mach/hurd/readlink.c b/sysdeps/mach/hurd/readlink.c
index 770462714f..2d75ef7725 100644
--- a/sysdeps/mach/hurd/readlink.c
+++ b/sysdeps/mach/hurd/readlink.c
@@ -31,7 +31,7 @@  __readlink (const char *file_name, char *buf, size_t len)
   file_t file;
   struct stat64 st;
 
-  file = __file_name_lookup (file_name, O_READ | O_NOLINK, 0);
+  file = __file_name_lookup (file_name, O_NOLINK, 0);
   if (file == MACH_PORT_NULL)
     return -1;
 
@@ -41,6 +41,9 @@  __readlink (const char *file_name, char *buf, size_t len)
       {
 	char *rbuf = buf;
 
+	__mach_port_deallocate (__mach_task_self (), file);
+	file = __file_name_lookup (file_name, O_READ | O_NOLINK, 0);
+
 	err = __io_read (file, &rbuf, &len, 0, len);
 	if (!err && rbuf != buf)
 	  {
diff --git a/sysdeps/mach/hurd/readlinkat.c b/sysdeps/mach/hurd/readlinkat.c
index 059aad9f58..113b92b732 100644
--- a/sysdeps/mach/hurd/readlinkat.c
+++ b/sysdeps/mach/hurd/readlinkat.c
@@ -32,7 +32,7 @@  readlinkat (int fd, const char *file_name, char *buf, size_t len)
   file_t file;
   struct stat64 st;
 
-  file = __file_name_lookup_at (fd, 0, file_name, O_READ | O_NOLINK, 0);
+  file = __file_name_lookup_at (fd, 0, file_name, O_NOLINK, 0);
   if (file == MACH_PORT_NULL)
     return -1;
 
@@ -42,6 +42,9 @@  readlinkat (int fd, const char *file_name, char *buf, size_t len)
       {
 	char *rbuf = buf;
 
+	__mach_port_deallocate (__mach_task_self (), file);
+	file = __file_name_lookup_at (fd, 0, file_name, O_READ | O_NOLINK, 0);
+
 	err = __io_read (file, &rbuf, &len, 0, len);
 	if (!err && rbuf != buf)
 	  {