btrfs: fix signed overflows in btrfs_sync_file
The calculation of range length in btrfs_sync_file leads to signed overflow. This was caught by PaX gcc SIZE_OVERFLOW plugin. https://forums.grsecurity.net/viewtopic.php?f=1&t=4284 The fsync call passes 0 and LLONG_MAX, the range length does not fit to loff_t and overflows, but the value is converted to u64 so it silently works as expected. The minimal fix is a typecast to u64, switching functions to take (start, end) instead of (start, len) would be more intrusive. Coccinelle script found that there's one more opencoded calculation of the length. <smpl> @@ loff_t start, end; @@ * end - start </smpl> CC: stable@vger.kernel.org Signed-off-by: David Sterba <dsterba@suse.com> Signed-off-by: Chris Mason <clm@fb.com>
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@ -1882,8 +1882,13 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
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struct btrfs_log_ctx ctx;
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int ret = 0;
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bool full_sync = 0;
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const u64 len = end - start + 1;
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u64 len;
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/*
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* The range length can be represented by u64, we have to do the typecasts
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* to avoid signed overflow if it's [0, LLONG_MAX] eg. from fsync()
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*/
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len = (u64)end - (u64)start + 1;
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trace_btrfs_sync_file(file, datasync);
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/*
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@ -2071,8 +2076,7 @@ int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
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}
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}
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if (!full_sync) {
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ret = btrfs_wait_ordered_range(inode, start,
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end - start + 1);
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ret = btrfs_wait_ordered_range(inode, start, len);
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if (ret) {
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btrfs_end_transaction(trans, root);
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goto out;
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