This is a note to let you know that I've just added the patch titled ipc/shm: handle removed segments gracefully in shm_mmap() to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ipc-shm-handle-removed-segments-gracefully-in-shm_mmap.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 1ac0b6dec656f3f78d1c3dd216fad84cb4d0a01e Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Date: Wed, 17 Feb 2016 13:11:35 -0800 Subject: ipc/shm: handle removed segments gracefully in shm_mmap() From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> commit 1ac0b6dec656f3f78d1c3dd216fad84cb4d0a01e upstream. 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 <stdlib.h> #include <sys/ipc.h> #include <sys/mman.h> #include <sys/shm.h> #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 <kirill.shutemov@xxxxxxxxxxxxxxx> Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx> Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- ipc/shm.c | 53 +++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 43 insertions(+), 10 deletions(-) --- a/ipc/shm.c +++ b/ipc/shm.c @@ -156,11 +156,12 @@ static inline struct shmid_kernel *shm_l 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_n } -/* 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_str 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_str 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, s 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) Patches currently in stable-queue which might be from kirill.shutemov@xxxxxxxxxxxxxxx are queue-4.4/mm-thp-khugepaged-call-pte-flush-at-the-time-of-collapse.patch queue-4.4/ipc-shm-handle-removed-segments-gracefully-in-shm_mmap.patch queue-4.4/drivers-scsi-sg.c-mark-vma-as-vm_io-to-prevent-migration.patch queue-4.4/mm-fix-mlock-accouting.patch queue-4.4/mm-replace-vma_lock_anon_vma-with-anon_vma_lock_read-write.patch queue-4.4/mm-fix-regression-in-remap_file_pages-emulation.patch queue-4.4/scsi-add-marvell-console-to-vpd-blacklist.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html