From ed67173357031d9a501e41b6be05cfc438f44adc Mon Sep 17 00:00:00 2001
From: Manfred Spraul <manfred@colorfullife.com>
Date: Sat, 30 Oct 2021 14:27:25 +0200
Subject: [PATCH 3/3] [DEBUG CODE] instrummented ipc/shm.c

Target: show that namespaces cannot outlive a shm segment.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
---
 ipc/shm.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/ipc/shm.c b/ipc/shm.c
index ebb25a8ecc58..6222d5b8acf6 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -126,6 +126,7 @@ static void do_shm_rmid(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 	shp = container_of(ipcp, struct shmid_kernel, shm_perm);
 	WARN_ON(ns != shp->ns);
 
+pr_info("do_shm_rmid(): shp %px: shp->shm_nattch %ld.\n", shp, shp->shm_nattch);
 	if (shp->shm_nattch) {
 		shp->shm_perm.mode |= SHM_DEST;
 		/* Do not find it any more */
@@ -138,9 +139,11 @@ static void do_shm_rmid(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 #ifdef CONFIG_IPC_NS
 void shm_exit_ns(struct ipc_namespace *ns)
 {
+pr_info("namespace %px: in exit_ns.\n", ns);
 	free_ipcs(ns, &shm_ids(ns), do_shm_rmid);
 	idr_destroy(&ns->ids[IPC_SHM_IDS].ipcs_idr);
 	rhashtable_destroy(&ns->ids[IPC_SHM_IDS].key_ht);
+pr_info("namespace %px: end of exit_ns.\n", ns);
 }
 #endif
 
@@ -287,6 +290,7 @@ static int __shm_open(struct vm_area_struct *vma)
 
 	shp->shm_atim = ktime_get_real_seconds();
 	ipc_update_pid(&shp->shm_lprid, task_tgid(current));
+pr_info("__shm_open(): before ++: shp %px, sfd->file %px: shp->shm_nattch %ld.\n", shp, sfd->file, shp->shm_nattch);
 	shp->shm_nattch++;
 	shm_unlock(shp);
 	return 0;
@@ -344,6 +348,7 @@ static void shm_destroy(struct ipc_namespace *ns, struct shmid_kernel *shp)
  */
 static bool shm_may_destroy(struct shmid_kernel *shp)
 {
+pr_info("shm_may_destroy(): shp %px: shp->shm_nattch %ld.\n", shp, shp->shm_nattch);
 	return (shp->shm_nattch == 0) &&
 	       (shp->ns->shm_rmid_forced ||
 		(shp->shm_perm.mode & SHM_DEST));
@@ -375,6 +380,7 @@ static void shm_close(struct vm_area_struct *vma)
 
 	ipc_update_pid(&shp->shm_lprid, task_tgid(current));
 	shp->shm_dtim = ktime_get_real_seconds();
+pr_info("shm_close(): before --: shp %px: shp->shm_nattch %ld.\n", shp, shp->shm_nattch);
 	shp->shm_nattch--;
 	if (shm_may_destroy(shp))
 		shm_destroy(ns, shp);
@@ -590,6 +596,7 @@ static int shm_release(struct inode *ino, struct file *file)
 {
 	struct shm_file_data *sfd = shm_file_data(file);
 
+pr_info("shm_release: file %px, put_ipc_ns().\n", sfd->file);
 	put_ipc_ns(sfd->ns);
 	fput(sfd->file);
 	shm_file_data(file) = NULL;
@@ -748,6 +755,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
 	shp->shm_segsz = size;
 	shp->shm_nattch = 0;
 	shp->shm_file = file;
+pr_info("newseg(): shp %px: shp->shm_nattch %ld ->shmfile %px.\n", shp, shp->shm_nattch, shp->shm_file);
 	shp->shm_creator = current;
 
 	/* ipc_addid() locks shp upon success. */
@@ -1588,6 +1596,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg,
 	 * detect shm ID reuse we need to compare the file pointers.
 	 */
 	base = get_file(shp->shm_file);
+pr_info("do_shmat(): shp %px: shp->shm_nattch %ld.\n", shp, shp->shm_nattch);
 	shp->shm_nattch++;
 	size = i_size_read(file_inode(base));
 	ipc_unlock_object(&shp->shm_perm);
@@ -1612,6 +1621,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg,
 	}
 
 	sfd->id = shp->shm_perm.id;
+pr_info("do_shmat(): shp %px: get_ipc_ns().\n", shp);
 	sfd->ns = get_ipc_ns(ns);
 	sfd->file = base;
 	sfd->vm_ops = NULL;
@@ -1651,6 +1661,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg,
 out_nattch:
 	down_write(&shm_ids(ns).rwsem);
 	shp = shm_lock(ns, shmid);
+pr_info("do_shmat() before --: shp %px: shp->shm_nattch %ld.\n", shp, shp->shm_nattch);
 	shp->shm_nattch--;
 
 	if (shm_may_destroy(shp))
-- 
2.31.1