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database/sql: fix panic with concurrent Conn and Close #68953

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@nklaassen nklaassen commented Aug 19, 2024 •
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The current implementation has a panic when the database is closed
concurrently with a new connection attempt.

connRequestSet.CloseAndRemoveAll sets connRequestSet.s to a nil slice.
If this happens between calls to connRequestSet.Add and
connRequestSet.Delete, there is a panic when trying to write to the nil
slice. This is sequence is likely to occur in DB.conn, where the mutex
is released between calls to db.connRequests.Add and
db.connRequests.Delete

This change updates connRequestSet.CloseAndRemoveAll to set the curIdx
to -1 for all pending requests before setting its internal slice to nil.
CloseAndRemoveAll already iterates the full slice to close all the request
channels. It seems appropriate to set curIdx to -1 before deleting the
slice for 3 reasons:

  1. connRequestSet.deleteIndex also sets curIdx to -1
  2. curIdx will not be relevant to anything after the slice is set to nil
  3. connRequestSet.Delete already checks for negative indices

Fixes #68949

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@nklaassen nklaassen mentioned this pull request Aug 20, 2024
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Patch Set 3:

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@nklaassen nklaassen force-pushed the fix-sql-conn-delete-panic branch from 258ad35 to 7d1a84e Compare August 22, 2024 19:10
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Patch Set 4: Commit-Queue+1

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@nklaassen
database/sql: fix panic with concurrent Conn and Close
7d26691 
The current implementation has a panic when the database is closed
concurrently with a new connection attempt.

connRequestSet.CloseAndRemoveAll sets connRequestSet.s to a nil slice.
If this happens between calls to connRequestSet.Add and
connRequestSet.Delete, there is a panic when trying to write to the nil
slice. This is sequence is likely to occur in DB.conn, where the mutex
is released between calls to db.connRequests.Add and
db.connRequests.Delete

This change updates connRequestSet.CloseAndRemoveAll to set the curIdx
to -1 for all pending requests before setting its internal slice to nil.
CloseAndRemoveAll already iterates the full slice to close all the request
channels. It seems appropriate to set curIdx to -1 before deleting the
slice for 3 reasons:
1. connRequestSet.deleteIndex also sets curIdx to -1
2. curIdx will not be relevant to anything after the slice is set to nil
3. connRequestSet.Delete already checks for negative indices

Fixes golang#68949
@nklaassen nklaassen force-pushed the fix-sql-conn-delete-panic branch from 7d1a84e to 7d26691 Compare August 22, 2024 23:32
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  • To change your code in response to feedback:
    • Push a new commit to the branch used by your GitHub PR.
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Patch Set 5: Commit-Queue+1

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Patch Set 5: Code-Review+2

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gopherbot pushed a commit that referenced this pull request Aug 24, 2024
@nklaassen @gopherbot
database/sql: fix panic with concurrent Conn and Close
08707d6 
The current implementation has a panic when the database is closed
concurrently with a new connection attempt.

connRequestSet.CloseAndRemoveAll sets connRequestSet.s to a nil slice.
If this happens between calls to connRequestSet.Add and
connRequestSet.Delete, there is a panic when trying to write to the nil
slice. This is sequence is likely to occur in DB.conn, where the mutex
is released between calls to db.connRequests.Add and
db.connRequests.Delete

This change updates connRequestSet.CloseAndRemoveAll to set the curIdx
to -1 for all pending requests before setting its internal slice to nil.
CloseAndRemoveAll already iterates the full slice to close all the request
channels. It seems appropriate to set curIdx to -1 before deleting the
slice for 3 reasons:
1. connRequestSet.deleteIndex also sets curIdx to -1
2. curIdx will not be relevant to anything after the slice is set to nil
3. connRequestSet.Delete already checks for negative indices

Fixes #68949

Change-Id: I6b7ebc5a71b67322908271d13865fa12f2469b87
GitHub-Last-Rev: 7d26691
GitHub-Pull-Request: #68953
Reviewed-on: https://go-review.googlesource.com/c/go/+/607238
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Commit-Queue: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
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This PR is being closed because golang.org/cl/607238 has been merged.

@gopherbot gopherbot closed this Aug 24, 2024
@nklaassen nklaassen deleted the fix-sql-conn-delete-panic branch August 24, 2024 02:43
gopherbot pushed a commit that referenced this pull request Aug 28, 2024
@nklaassen @prattmic
[release-branch.go1.23] database/sql: fix panic with concurrent Conn …
6de5a71 
…and Close

The current implementation has a panic when the database is closed
concurrently with a new connection attempt.

connRequestSet.CloseAndRemoveAll sets connRequestSet.s to a nil slice.
If this happens between calls to connRequestSet.Add and
connRequestSet.Delete, there is a panic when trying to write to the nil
slice. This is sequence is likely to occur in DB.conn, where the mutex
is released between calls to db.connRequests.Add and
db.connRequests.Delete

This change updates connRequestSet.CloseAndRemoveAll to set the curIdx
to -1 for all pending requests before setting its internal slice to nil.
CloseAndRemoveAll already iterates the full slice to close all the request
channels. It seems appropriate to set curIdx to -1 before deleting the
slice for 3 reasons:
1. connRequestSet.deleteIndex also sets curIdx to -1
2. curIdx will not be relevant to anything after the slice is set to nil
3. connRequestSet.Delete already checks for negative indices

For #68949
Fixes #69041

Change-Id: I6b7ebc5a71b67322908271d13865fa12f2469b87
GitHub-Last-Rev: 7d26691
GitHub-Pull-Request: #68953
Reviewed-on: https://go-review.googlesource.com/c/go/+/607238
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Commit-Queue: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
(cherry picked from commit 08707d6)
Reviewed-on: https://go-review.googlesource.com/c/go/+/609255
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database/sql: panic in database/sql.(*connRequestSet).deleteIndex
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