Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752088AbbKKI5H (ORCPT ); Wed, 11 Nov 2015 03:57:07 -0500 Received: from mga01.intel.com ([192.55.52.88]:57392 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751082AbbKKI5F (ORCPT ); Wed, 11 Nov 2015 03:57:05 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,274,1444719600"; d="scan'208";a="598158652" From: "Kirill A. Shutemov" To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dmitry Vyukov , "Kirill A. Shutemov" , Davidlohr Bueso Subject: [PATCH, RESEND] ipc/shm: handle removed segments gracefully in shm_mmap() Date: Wed, 11 Nov 2015 10:57:00 +0200 Message-Id: <1447232220-36879-1-git-send-email-kirill.shutemov@linux.intel.com> X-Mailer: git-send-email 2.6.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4132 Lines: 158 remap_file_pages(2) emulation can reach file which represents removed IPC ID as long as a memory segment is mapped. It breaks expectations of IPC subsystem. Test case (rewritten to be more human readable, originally autogenerated by syzkaller[1]): #define _GNU_SOURCE #include #include #include #include #define PAGE_SIZE 4096 int main() { int id; void *p; id = shmget(IPC_PRIVATE, 3 * PAGE_SIZE, 0); p = shmat(id, NULL, 0); shmctl(id, IPC_RMID, NULL); remap_file_pages(p, 3 * PAGE_SIZE, 0, 7, 0); return 0; } The patch changes shm_mmap() and code around shm_lock() to propagate locking error back to caller of shm_mmap(). [1] http://github.com/google/syzkaller Signed-off-by: Kirill A. Shutemov Reported-by: Dmitry Vyukov Cc: Davidlohr Bueso --- ipc/shm.c | 53 +++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 43 insertions(+), 10 deletions(-) diff --git a/ipc/shm.c b/ipc/shm.c index 41787276e141..3174634ca4e5 100644 --- 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 +187,33 @@ 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); + 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 +276,14 @@ 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 +291,7 @@ 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 +413,25 @@ 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 + * removed IPC ID: propogate shm_lock() 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) -- 2.6.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/