svn commit: r364990 - head/sys/kern

[Kyle Evans]

Author: kevans
Date: Mon Aug 31 15:07:15 2020
New Revision: 364990
URL: https://svnweb.freebsd.org/changeset/base/364990

Log:
  posixshm: fix setting of shm_flags
  
  Noted in D24652, we currently set shmfd->shm_flags on every
  shm_open()/shm_open2(). This wasn't properly thought out; one shouldn't be
  able to specify incompatible flags on subsequent opens of non-anon shm.
  
  Move setting of shm_flags explicitly to the two places shmfd are created, as
  we do with seals, and validate when we're opening a pre-existing mapping
  that we've either passed no flags or we've passed the exact same flags as
  the first time.
  
  Reviewed by:	kib, markj
  Differential Revision:	https://reviews.freebsd.org/D26242

Modified:
  head/sys/kern/uipc_shm.c

Modified: head/sys/kern/uipc_shm.c
==============================================================================
--- head/sys/kern/uipc_shm.c	Mon Aug 31 15:03:23 2020	(r364989)
+++ head/sys/kern/uipc_shm.c	Mon Aug 31 15:07:15 2020	(r364990)
@@ -833,6 +833,7 @@ kern_shm_open2(struct thread *td, const char *userpath
 		}
 		shmfd = shm_alloc(td->td_ucred, cmode);
 		shmfd->shm_seals = initial_seals;
+		shmfd->shm_flags = shmflags;
 	} else {
 		error = shm_copyin_path(td, userpath, &path);
 		if (error != 0) {
@@ -855,6 +856,7 @@ kern_shm_open2(struct thread *td, const char *userpath
 #endif
 					shmfd = shm_alloc(td->td_ucred, cmode);
 					shmfd->shm_seals = initial_seals;
+					shmfd->shm_flags = shmflags;
 					shm_insert(path, fnv, shmfd);
 #ifdef MAC
 				}
@@ -898,6 +900,8 @@ kern_shm_open2(struct thread *td, const char *userpath
 			else if ((flags & (O_CREAT | O_EXCL)) ==
 			    (O_CREAT | O_EXCL))
 				error = EEXIST;
+			else if (shmflags != 0 && shmflags != shmfd->shm_flags)
+				error = EINVAL;
 			else {
 #ifdef MAC
 				error = mac_posixshm_check_open(td->td_ucred,
@@ -947,7 +951,6 @@ kern_shm_open2(struct thread *td, const char *userpath
 		}
 	}
 
-	shmfd->shm_flags = shmflags;
 	finit(fp, FFLAGS(flags & O_ACCMODE), DTYPE_SHM, shmfd, &shm_ops);
 
 	td->td_retval[0] = fd;