power: supply: ltc2941-battery-gauge: fix use-after-free

[sagit-ice-cold/kernel_xiaomi_msm8998.git] / ipc / shm.c

diff --git a/ipc/shm.c b/ipc/shm.c
index 4178727..32974cf 100644 (file)
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -156,11 +156,12 @@ static inline struct shmid_kernel *shm_lock(struct ipc_namespace *ns, int id)
        struct kern_ipc_perm *ipcp = ipc_lock(&shm_ids(ns), id);
 
        /*
-        * We raced in the idr lookup or with shm_destroy().  Either way, the
-        * ID is busted.
+        * Callers of shm_lock() must validate the status of the returned ipc
+        * object pointer (as returned by ipc_lock()), and error out as
+        * appropriate.
         */
-       WARN_ON(IS_ERR(ipcp));
-
+       if (IS_ERR(ipcp))
+               return (void *)ipcp;
        return container_of(ipcp, struct shmid_kernel, shm_perm);
 }
 
@@ -186,18 +187,39 @@ static inline void shm_rmid(struct ipc_namespace *ns, struct shmid_kernel *s)
 }
 
 
-/* This is called by fork, once for every shm attach. */
-static void shm_open(struct vm_area_struct *vma)
+static int __shm_open(struct vm_area_struct *vma)
 {
        struct file *file = vma->vm_file;
        struct shm_file_data *sfd = shm_file_data(file);
        struct shmid_kernel *shp;
 
        shp = shm_lock(sfd->ns, sfd->id);
+
+       if (IS_ERR(shp))
+               return PTR_ERR(shp);
+
+       if (shp->shm_file != sfd->file) {
+               /* ID was reused */
+               shm_unlock(shp);
+               return -EINVAL;
+       }
+
        shp->shm_atim = get_seconds();
        shp->shm_lprid = task_tgid_vnr(current);
        shp->shm_nattch++;
        shm_unlock(shp);
+       return 0;
+}
+
+/* This is called by fork, once for every shm attach. */
+static void shm_open(struct vm_area_struct *vma)
+{
+       int err = __shm_open(vma);
+       /*
+        * We raced in the idr lookup or with shm_destroy().
+        * Either way, the ID is busted.
+        */
+       WARN_ON_ONCE(err);
 }
 
 /*
@@ -260,6 +282,14 @@ static void shm_close(struct vm_area_struct *vma)
        down_write(&shm_ids(ns).rwsem);
        /* remove from the list of attaches of the shm segment */
        shp = shm_lock(ns, sfd->id);
+
+       /*
+        * We raced in the idr lookup or with shm_destroy().
+        * Either way, the ID is busted.
+        */
+       if (WARN_ON_ONCE(IS_ERR(shp)))
+               goto done; /* no-op */
+
        shp->shm_lprid = task_tgid_vnr(current);
        shp->shm_dtim = get_seconds();
        shp->shm_nattch--;
@@ -267,6 +297,7 @@ static void shm_close(struct vm_area_struct *vma)
                shm_destroy(ns, shp);
        else
                shm_unlock(shp);
+done:
        up_write(&shm_ids(ns).rwsem);
 }
 
@@ -388,17 +419,26 @@ static int shm_mmap(struct file *file, struct vm_area_struct *vma)
        struct shm_file_data *sfd = shm_file_data(file);
        int ret;
 
+       /*
+        * In case of remap_file_pages() emulation, the file can represent an
+        * IPC ID that was removed, and possibly even reused by another shm
+        * segment already.  Propagate this case as an error to caller.
+        */
+       ret =__shm_open(vma);
+       if (ret)
+               return ret;
+
        ret = sfd->file->f_op->mmap(sfd->file, vma);
-       if (ret != 0)
+       if (ret) {
+               shm_close(vma);
                return ret;
+       }
        sfd->vm_ops = vma->vm_ops;
 #ifdef CONFIG_MMU
        WARN_ON(!sfd->vm_ops->fault);
 #endif
        vma->vm_ops = &shm_vm_ops;
-       shm_open(vma);
-
-       return ret;
+       return 0;
 }
 
 static int shm_release(struct inode *ino, struct file *file)
@@ -406,6 +446,7 @@ static int shm_release(struct inode *ino, struct file *file)
        struct shm_file_data *sfd = shm_file_data(file);
 
        put_ipc_ns(sfd->ns);
+       fput(sfd->file);
        shm_file_data(file) = NULL;
        kfree(sfd);
        return 0;
@@ -1050,8 +1091,8 @@ out_unlock1:
  * "raddr" thing points to kernel space, and there has to be a wrapper around
  * this.
  */
-long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
-             unsigned long shmlba)
+long do_shmat(int shmid, char __user *shmaddr, int shmflg,
+             ulong *raddr, unsigned long shmlba)
 {
        struct shmid_kernel *shp;
        unsigned long addr;
@@ -1072,9 +1113,17 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
                goto out;
        else if ((addr = (ulong)shmaddr)) {
                if (addr & (shmlba - 1)) {
-                       if (shmflg & SHM_RND)
-                               addr &= ~(shmlba - 1);     /* round down */
-                       else
+                       if (shmflg & SHM_RND) {
+                               addr &= ~(shmlba - 1);  /* round down */
+
+                               /*
+                                * Ensure that the round-down is non-nil
+                                * when remapping. This can happen for
+                                * cases when addr < shmlba.
+                                */
+                               if (!addr && (shmflg & SHM_REMAP))
+                                       goto out;
+                       } else
 #ifndef __ARCH_FORCE_SHMLBA
                                if (addr & ~PAGE_MASK)
 #endif
@@ -1160,7 +1209,16 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
        file->f_mapping = shp->shm_file->f_mapping;
        sfd->id = shp->shm_perm.id;
        sfd->ns = get_ipc_ns(ns);
-       sfd->file = shp->shm_file;
+       /*
+        * We need to take a reference to the real shm file to prevent the
+        * pointer from becoming stale in cases where the lifetime of the outer
+        * file extends beyond that of the shm segment.  It's not usually
+        * possible, but it can happen during remap_file_pages() emulation as
+        * that unmaps the memory, then does ->mmap() via file reference only.
+        * We'll deny the ->mmap() if the shm segment was since removed, but to
+        * detect shm ID reuse we need to compare the file pointers.
+        */
+       sfd->file = get_file(shp->shm_file);
        sfd->vm_ops = NULL;
 
        err = security_mmap_file(file, prot, flags);