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Fix #80384: limit read buffer size #6444

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Fix #80384: limit read buffer size #6444

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adamjseitz
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In the case of a stream with no filters, php_stream_fill_read_buffer
only reads stream->chunk_size into the read buffer. If the stream has
filters attached, it could unnecessarily buffer a large amount of data.

With this change, php_stream_fill_read_buffer only proceeds until either
the requested size or stream->chunk_size is available in the read buffer.

Bug report at https://bugs.php.net/bug.php?id=80384

@cmb69
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cmb69 commented Nov 23, 2020

This looks reasonable to me, but I'm very reluctant to target PHP-7.3 since 7.3.26 is going to be the last bug fix release, and if that would break something, we couldn't (easily) revert.

Also, consider to add a test (using the string.rot13 filter, or so), which checks that the memory usage is not totally off.

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Alright, I'll get a test added and update the PR against 7.4 when I get a chance.

@adamjseitz adamjseitz changed the base branch from PHP-7.3 to PHP-7.4 December 2, 2020 00:09
@adamjseitz adamjseitz marked this pull request as draft December 2, 2020 01:47
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nikic commented Dec 7, 2020

Is this marked as a draft intentionally?

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Is this marked as a draft intentionally?

Yes, there seem to be tests failing on AppVeyor, so I need to figure that out, still.

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cmb69 commented Dec 15, 2020

The former AppVeyor build ran against PHP-7.3; I just retriggered that CI.

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cmb69 commented Dec 15, 2020

There is only a single test failure on AppVeyor now. I'll try to have a closer look unless someone beats me to it.

@adamjseitz @cmb69
Fix #80384: limit read buffer size
252bc44 
In the case of a stream with no filters, php_stream_fill_read_buffer
only reads stream->chunk_size into the read buffer. If the stream has
filters attached, it could unnecessarily buffer a large amount of data.

With this change, php_stream_fill_read_buffer only proceeds until either
the requested size or stream->chunk_size is available in the read buffer.
@cmb69
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cmb69 commented Dec 16, 2020

That other test failure is actually to be expected; the test expectations need to be adjusted. It failed only on AppVeyor, because there the diff is applied to the base branch, but on the other CIs the PR is tested as is. I've rebased onto PHP-7.4.

cmb69
cmb69 reviewed Dec 16, 2020
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Thank you for the PR! The fix looks good to me, but the test could be improved.

@adamjseitz adamjseitz marked this pull request as ready for review December 19, 2020 15:05
@adamjseitz adamjseitz requested a review from cmb69 December 19, 2020 15:12
@adamjseitz
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Thank you for the PR! The fix looks good to me, but the test could be improved.

Thanks for the review, and good feedback. Updated with those fixed.

cmb69
cmb69 approved these changes Dec 23, 2020
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Thank you! I'm going to merge, fixing the other test's expectations right away.

@php-pulls php-pulls closed this in 70dfbe0 Dec 23, 2020
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@adamjseitz @cmb69 @nikic