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authorLinus Torvalds <torvalds@linux-foundation.org>2021-10-24 09:48:33 -1000
committerLinus Torvalds <torvalds@linux-foundation.org>2021-10-24 09:48:33 -1000
commit87066fdd2e30fe9dd531125d95257c118a74617e (patch)
tree889339bdce44c612c179d28ab9209978e85eef48
parentb20078fd69a3da08d85c79b95101cf25c4afcc97 (diff)
downloadlinux-87066fdd2e30fe9dd531125d95257c118a74617e.tar.gz
Revert "mm/secretmem: use refcount_t instead of atomic_t"
This reverts commit 110860541f443f950c1274f217a1a3e298670a33. Converting the "secretmem_users" counter to a refcount is incorrect, because a refcount is special in zero and can't just be incremented (but a count of users is not, and "no users" is actually perfectly valid and not a sign of a free'd resource). Reported-by: syzbot+75639e6a0331cd61d3e2@syzkaller.appspotmail.com Cc: Jordy Zomer <jordy@pwning.systems> Cc: Kees Cook <keescook@chromium.org>, Cc: Jordy Zomer <jordy@jordyzomer.github.io> Cc: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/secretmem.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/mm/secretmem.c b/mm/secretmem.c
index 1fea68b8d5a6..030f02ddc7c1 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -18,7 +18,6 @@
#include <linux/secretmem.h>
#include <linux/set_memory.h>
#include <linux/sched/signal.h>
-#include <linux/refcount.h>
#include <uapi/linux/magic.h>
@@ -41,11 +40,11 @@ module_param_named(enable, secretmem_enable, bool, 0400);
MODULE_PARM_DESC(secretmem_enable,
"Enable secretmem and memfd_secret(2) system call");
-static refcount_t secretmem_users;
+static atomic_t secretmem_users;
bool secretmem_active(void)
{
- return !!refcount_read(&secretmem_users);
+ return !!atomic_read(&secretmem_users);
}
static vm_fault_t secretmem_fault(struct vm_fault *vmf)
@@ -104,7 +103,7 @@ static const struct vm_operations_struct secretmem_vm_ops = {
static int secretmem_release(struct inode *inode, struct file *file)
{
- refcount_dec(&secretmem_users);
+ atomic_dec(&secretmem_users);
return 0;
}
@@ -218,7 +217,7 @@ SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
file->f_flags |= O_LARGEFILE;
fd_install(fd, file);
- refcount_inc(&secretmem_users);
+ atomic_inc(&secretmem_users);
return fd;
err_put_fd: