[PATCH] mm: Check NULL pointer Dereference in mm/filemap.c
in [Kernel]
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From: wzt.wzt on 26 Jul 2010 04:30 mapping->a_ops->direct_IO() is not checked, if it's a NULL pointer, that will casue an oops. pagecache_write_begin/end is exported to other functions, so they need to check null pointer before use them. Signed-off-by: Zhitong Wang <zhitong.wangzt(a)alibaba-inc.com> --- mm/filemap.c | 13 +++++++++++++ 1 files changed, 13 insertions(+), 0 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 20e5642..e81e264 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1300,6 +1300,9 @@ generic_file_aio_read(struct kiocb *iocb, const struct iovec *iov, retval = filemap_write_and_wait_range(mapping, pos, pos + iov_length(iov, nr_segs) - 1); if (!retval) { + if (unlikely(!mapping->a_ops || + !mapping->a_ops->direct_IO)) + goto out; retval = mapping->a_ops->direct_IO(READ, iocb, iov, pos, nr_segs); } @@ -1581,6 +1584,8 @@ retry_find: return ret | VM_FAULT_LOCKED; no_cached_page: + if (unlikely(!mapping->a_ops || !mapping->a_ops->readpage)) + return VM_FAULT_SIGBUS; /* * We're only likely to ever get here if MADV_RANDOM is in * effect. @@ -2103,6 +2108,8 @@ int pagecache_write_begin(struct file *file, struct address_space *mapping, { const struct address_space_operations *aops = mapping->a_ops; + if (unlikely(!aops || !aops->write_begin)) + return -EINVAL; return aops->write_begin(file, mapping, pos, len, flags, pagep, fsdata); } @@ -2114,6 +2121,9 @@ int pagecache_write_end(struct file *file, struct address_space *mapping, { const struct address_space_operations *aops = mapping->a_ops; + if (unlikely(!aops || !aops->write_end)) + return -EINVAL; + mark_page_accessed(page); return aops->write_end(file, mapping, pos, len, copied, page, fsdata); } @@ -2161,6 +2171,9 @@ generic_file_direct_write(struct kiocb *iocb, const struct iovec *iov, } } + if (unlikely(!mapping->a_ops || !mapping->a_ops->direct_IO)) + goto out; + written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs); /* -- 1.6.5.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |