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31b4beb473
Commitc01d5b3007("shmem: get_unmapped_area align huge page") makes use of shm_get_unmapped_area() in shm_file_operations() unconditional to CONFIG_MMU. As Tony Battersby pointed this can lead NULL-pointer dereference on machine with CONFIG_MMU=y and CONFIG_SHMEM=n. In this case ipc/shm is backed by ramfs which doesn't provide f_op->get_unmapped_area for configurations with MMU. The solution is to provide dummy f_op->get_unmapped_area for ramfs when CONFIG_MMU=y, which just call current->mm->get_unmapped_area(). Fixes:c01d5b3007("shmem: get_unmapped_area align huge page") Link: http://lkml.kernel.org/r/20160912102704.140442-1-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Tony Battersby <tonyb@cybernetics.com> Tested-by: Tony Battersby <tonyb@cybernetics.com> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> [4.7.x] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
56 lines
1.6 KiB
C
56 lines
1.6 KiB
C
/* file-mmu.c: ramfs MMU-based file operations
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*
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* Resizable simple ram filesystem for Linux.
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*
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* Copyright (C) 2000 Linus Torvalds.
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* 2000 Transmeta Corp.
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*
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* Usage limits added by David Gibson, Linuxcare Australia.
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* This file is released under the GPL.
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*/
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/*
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* NOTE! This filesystem is probably most useful
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* not as a real filesystem, but as an example of
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* how virtual filesystems can be written.
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*
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* It doesn't get much simpler than this. Consider
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* that this file implements the full semantics of
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* a POSIX-compliant read-write filesystem.
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*
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* Note in particular how the filesystem does not
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* need to implement any data structures of its own
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* to keep track of the virtual data: using the VFS
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* caches is sufficient.
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*/
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/ramfs.h>
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#include <linux/sched.h>
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#include "internal.h"
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static unsigned long ramfs_mmu_get_unmapped_area(struct file *file,
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unsigned long addr, unsigned long len, unsigned long pgoff,
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unsigned long flags)
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{
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return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
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}
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const struct file_operations ramfs_file_operations = {
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.read_iter = generic_file_read_iter,
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.write_iter = generic_file_write_iter,
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.mmap = generic_file_mmap,
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.fsync = noop_fsync,
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.splice_read = generic_file_splice_read,
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.splice_write = iter_file_splice_write,
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.llseek = generic_file_llseek,
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.get_unmapped_area = ramfs_mmu_get_unmapped_area,
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};
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const struct inode_operations ramfs_file_inode_operations = {
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.setattr = simple_setattr,
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.getattr = simple_getattr,
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};
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