diff mbox series

[v1] nscd: Fix double free in netgroupcache [BZ #27462]

Message ID xnpn0n4zrd.fsf@greed.delorie.com
State Committed
Commit dca565886b5e8bd7966e15f0ca42ee5cff686673
Delegated to: Siddhesh Poyarekar
Headers show
Series [v1] nscd: Fix double free in netgroupcache [BZ #27462] | expand

Commit Message

DJ Delorie Feb. 25, 2021, 9:13 p.m. UTC
In commit 745664bd798ec8fd50438605948eea594179fba1 a use-after-free
was fixed, but this led to an occasional double-free.  This patch
tracks the "live" allocation better.

Tested manually by a third party.

Related: RHBZ 1927877
---
 nscd/netgroupcache.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Siddhesh Poyarekar March 1, 2021, 7:48 a.m. UTC | #1
On 2/26/21 2:43 AM, DJ Delorie via Libc-alpha wrote:
> 
> In commit 745664bd798ec8fd50438605948eea594179fba1 a use-after-free
> was fixed, but this led to an occasional double-free.  This patch
> tracks the "live" allocation better.
> 
> Tested manually by a third party.
> 
> Related: RHBZ 1927877

Looks fine to me.  Now that we have container testing, we should add 
tests for nscd, especially since nscd doesn't seem to be going anywhere.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

Siddhesh
Carlos O'Donell March 2, 2021, 5:03 p.m. UTC | #2
On 2/25/21 4:13 PM, DJ Delorie via Libc-alpha wrote:
> 
> In commit 745664bd798ec8fd50438605948eea594179fba1 a use-after-free
> was fixed, but this led to an occasional double-free.  This patch
> tracks the "live" allocation better.
> 
> Tested manually by a third party.

This looks like it should be logically the correct fix. There are only
two xrealloc's that I see that could impact the buffer reuse here and
we need to track the update to the pointer.

LGTM.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> Related: RHBZ 1927877
> ---
>  nscd/netgroupcache.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/nscd/netgroupcache.c b/nscd/netgroupcache.c
> index dba6ceec1b..ad2daddafd 100644
> --- a/nscd/netgroupcache.c
> +++ b/nscd/netgroupcache.c
> @@ -248,7 +248,7 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
>  					     : NULL);
>  				    ndomain = (ndomain ? newbuf + ndomaindiff
>  					       : NULL);
> -				    buffer = newbuf;
> +				    *tofreep = buffer = newbuf;
>  				  }
>  
>  				nhost = memcpy (buffer + bufused,
> @@ -319,7 +319,7 @@ addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
>  		    else if (status == NSS_STATUS_TRYAGAIN && e == ERANGE)
>  		      {
>  			buflen *= 2;
> -			buffer = xrealloc (buffer, buflen);
> +			*tofreep = buffer = xrealloc (buffer, buflen);
>  		      }
>  		    else if (status == NSS_STATUS_RETURN
>  			     || status == NSS_STATUS_NOTFOUND
>
Andreas Schwab March 3, 2021, 12:19 p.m. UTC | #3
Please add the CVE reference.

Andreas.
diff mbox series

Patch

diff --git a/nscd/netgroupcache.c b/nscd/netgroupcache.c
index dba6ceec1b..ad2daddafd 100644
--- a/nscd/netgroupcache.c
+++ b/nscd/netgroupcache.c
@@ -248,7 +248,7 @@  addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
 					     : NULL);
 				    ndomain = (ndomain ? newbuf + ndomaindiff
 					       : NULL);
-				    buffer = newbuf;
+				    *tofreep = buffer = newbuf;
 				  }
 
 				nhost = memcpy (buffer + bufused,
@@ -319,7 +319,7 @@  addgetnetgrentX (struct database_dyn *db, int fd, request_header *req,
 		    else if (status == NSS_STATUS_TRYAGAIN && e == ERANGE)
 		      {
 			buflen *= 2;
-			buffer = xrealloc (buffer, buflen);
+			*tofreep = buffer = xrealloc (buffer, buflen);
 		      }
 		    else if (status == NSS_STATUS_RETURN
 			     || status == NSS_STATUS_NOTFOUND