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Bug fix: reset io_last_written on c->buf resize to prevent stale pointers#2786

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hpatro merged 1 commit intovalkey-io:unstablefrom
xbasel:fixCbuf
Oct 30, 2025
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Bug fix: reset io_last_written on c->buf resize to prevent stale pointers#2786
hpatro merged 1 commit intovalkey-io:unstablefrom
xbasel:fixCbuf

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@xbasel xbasel commented Oct 30, 2025

Fixes an assert crash in _writeToClient():

serverAssert(c->io_last_written.data_len == 0 ||
             c->io_last_written.buf == c->buf);

The issue occurs when clientsCronResizeOutputBuffer() grows or reallocates c->buf while io_last_written still points to the old buffer and data_len is non-zero. On the next write, both conditions in the assertion become false.

Reset io_last_written when resizing the output buffer to prevent stale pointers and keep state consistent.

fixes #2769

@xbasel xbasel marked this pull request as draft October 30, 2025 19:12
@madolson madolson requested a review from hpatro October 30, 2025 19:17
@madolson madolson moved this to Todo in Valkey 9.0 Oct 30, 2025
@xbasel
Bug fix: reset io_last_written on c->buf resize to prevent stale poin…
8d00054 
…ters

Fixes an assert crash in _writeToClient():

    serverAssert(c->io_last_written.data_len == 0 ||
                 c->io_last_written.buf == c->buf);

The issue occurs when clientsCronResizeOutputBuffer() grows or reallocates
c->buf while io_last_written still points to the old buffer and data_len is
non-zero. On the next write, both conditions in the assertion become false.

Reset io_last_written when resizing the output buffer to prevent stale pointers
and keep state consistent.

fixes valkey-io#2769

Signed-off-by: xbasel <103044017+xbasel@users.noreply.github.com>
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codecov bot commented Oct 30, 2025 •
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.26%. Comparing base (864de55) to head (8d00054).
⚠️ Report is 1 commits behind head on unstable.

Additional details and impacted files 
@@             Coverage Diff              @@
##           unstable    #2786      +/-   ##
============================================
- Coverage     72.42%   72.26%   -0.16%     
============================================
  Files           128      128              
  Lines         70209    70211       +2     
============================================
- Hits          50847    50740     -107     
- Misses        19362    19471     +109
Files with missing lines Coverage Δ
src/server.c 88.48% <100.00%> (+<0.01%) ⬆️

... and 13 files with indirect coverage changes

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@xbasel xbasel marked this pull request as ready for review October 30, 2025 19:51
hpatro
hpatro reviewed Oct 30, 2025
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QQ: Don't we need to update any of the other fields of c->io_last_written ?

My bad. It's just the change in reference. data written so far is the same.

@hpatro hpatro merged commit f54818c into valkey-io:unstable Oct 30, 2025
55 checks passed
@github-project-automation github-project-automation bot moved this from Todo to To be backported in Valkey 9.0 Oct 30, 2025
zhijun42 pushed a commit to zhijun42/valkey that referenced this pull request Nov 15, 2025
@xbasel @zhijun42
Bug fix: reset io_last_written on c->buf resize to prevent stale poin…
52dc7f1 
…ters (valkey-io#2786)

Fixes an assert crash in _writeToClient():

    serverAssert(c->io_last_written.data_len == 0 ||
                 c->io_last_written.buf == c->buf);

The issue occurs when clientsCronResizeOutputBuffer() grows or
reallocates c->buf while io_last_written still points to the old buffer
and data_len is non-zero. On the next write, both conditions in the
assertion become false.

Reset io_last_written when resizing the output buffer to prevent stale
pointers and keep state consistent.

fixes valkey-io#2769

Signed-off-by: xbasel <103044017+xbasel@users.noreply.github.com>
zhijun42 pushed a commit to zhijun42/valkey that referenced this pull request Nov 15, 2025
@xbasel @zhijun42
Bug fix: reset io_last_written on c->buf resize to prevent stale poin…
6ecbb09 
…ters (valkey-io#2786)

Fixes an assert crash in _writeToClient():

    serverAssert(c->io_last_written.data_len == 0 ||
                 c->io_last_written.buf == c->buf);

The issue occurs when clientsCronResizeOutputBuffer() grows or
reallocates c->buf while io_last_written still points to the old buffer
and data_len is non-zero. On the next write, both conditions in the
assertion become false.

Reset io_last_written when resizing the output buffer to prevent stale
pointers and keep state consistent.

fixes valkey-io#2769

Signed-off-by: xbasel <103044017+xbasel@users.noreply.github.com>
zhijun42 pushed a commit to zhijun42/valkey that referenced this pull request Nov 28, 2025
@xbasel @zhijun42
Bug fix: reset io_last_written on c->buf resize to prevent stale poin…
888451e 
…ters (valkey-io#2786)

Fixes an assert crash in _writeToClient():

    serverAssert(c->io_last_written.data_len == 0 ||
                 c->io_last_written.buf == c->buf);

The issue occurs when clientsCronResizeOutputBuffer() grows or
reallocates c->buf while io_last_written still points to the old buffer
and data_len is non-zero. On the next write, both conditions in the
assertion become false.

Reset io_last_written when resizing the output buffer to prevent stale
pointers and keep state consistent.

fixes valkey-io#2769

Signed-off-by: xbasel <103044017+xbasel@users.noreply.github.com>
zhijun42 pushed a commit to zhijun42/valkey that referenced this pull request Nov 28, 2025
@xbasel @zhijun42
Bug fix: reset io_last_written on c->buf resize to prevent stale poin…
3ef1c1f 
…ters (valkey-io#2786)

Fixes an assert crash in _writeToClient():

    serverAssert(c->io_last_written.data_len == 0 ||
                 c->io_last_written.buf == c->buf);

The issue occurs when clientsCronResizeOutputBuffer() grows or
reallocates c->buf while io_last_written still points to the old buffer
and data_len is non-zero. On the next write, both conditions in the
assertion become false.

Reset io_last_written when resizing the output buffer to prevent stale
pointers and keep state consistent.

fixes valkey-io#2769

Signed-off-by: xbasel <103044017+xbasel@users.noreply.github.com>
zhijun42 pushed a commit to zhijun42/valkey that referenced this pull request Nov 28, 2025
@xbasel @zhijun42
Bug fix: reset io_last_written on c->buf resize to prevent stale poin…
9e3e126 
…ters (valkey-io#2786)

Fixes an assert crash in _writeToClient():

    serverAssert(c->io_last_written.data_len == 0 ||
                 c->io_last_written.buf == c->buf);

The issue occurs when clientsCronResizeOutputBuffer() grows or
reallocates c->buf while io_last_written still points to the old buffer
and data_len is non-zero. On the next write, both conditions in the
assertion become false.

Reset io_last_written when resizing the output buffer to prevent stale
pointers and keep state consistent.

fixes valkey-io#2769

Signed-off-by: xbasel <103044017+xbasel@users.noreply.github.com>
@zuiderkwast zuiderkwast moved this from To be backported to 9.0.1 (WIP) in Valkey 9.0 Dec 4, 2025
zuiderkwast pushed a commit to zuiderkwast/placeholderkv that referenced this pull request Dec 4, 2025
@xbasel @zuiderkwast
Bug fix: reset io_last_written on c->buf resize to prevent stale poin…
6510966 
…ters (valkey-io#2786)

Fixes an assert crash in _writeToClient():

    serverAssert(c->io_last_written.data_len == 0 ||
                 c->io_last_written.buf == c->buf);

The issue occurs when clientsCronResizeOutputBuffer() grows or
reallocates c->buf while io_last_written still points to the old buffer
and data_len is non-zero. On the next write, both conditions in the
assertion become false.

Reset io_last_written when resizing the output buffer to prevent stale
pointers and keep state consistent.

fixes valkey-io#2769

Signed-off-by: xbasel <103044017+xbasel@users.noreply.github.com>
@zuiderkwast zuiderkwast mentioned this pull request Dec 4, 2025
Merged
zuiderkwast pushed a commit that referenced this pull request Dec 9, 2025
@xbasel @zuiderkwast
Bug fix: reset io_last_written on c->buf resize to prevent stale poin…
1ca63e1 
…ters (#2786)

Fixes an assert crash in _writeToClient():

    serverAssert(c->io_last_written.data_len == 0 ||
                 c->io_last_written.buf == c->buf);

The issue occurs when clientsCronResizeOutputBuffer() grows or
reallocates c->buf while io_last_written still points to the old buffer
and data_len is non-zero. On the next write, both conditions in the
assertion become false.

Reset io_last_written when resizing the output buffer to prevent stale
pointers and keep state consistent.

fixes #2769

Signed-off-by: xbasel <103044017+xbasel@users.noreply.github.com>
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[CRASH] Assertion failure in networking.c after upgrading from 8.1.4 to 9.0.0 (PUB/SUB, I/O threads enabled)

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