upstream: add null check for stream cleanup #10749
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Signed-off-by: Zhihong Lin <zhiholin@amazon.com>
WalkthroughReplace the unconditional removal of an upstream node from its list with a guarded removal: Changes
Sequence Diagram(s)sequenceDiagram
participant Caller
participant flb_upstream_destroy
Caller->>flb_upstream_destroy: destroy(u)
alt node is linked (mk_list_is_set == true)
flb_upstream_destroy->>flb_upstream_destroy: mk_list_del(&u->base._head)
else node not linked
Note right of flb_upstream_destroy: Skip mk_list_del
end
flb_upstream_destroy-->>Caller: return
Estimated code review effort🎯 2 (Simple) | ⏱️ ~10 minutes Poem
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Actionable comments posted: 0
🧹 Nitpick comments (1)
src/flb_upstream.c (1)
683-687: Optional: document the rationale for future maintainers.A short comment here will save time for the next person who touches this code.
Apply this diff to add a brief explanation:
- if (u->base._head.next != NULL && u->base._head.prev != NULL) { + /* Unlink only if the node was linked. For non-linked nodes, + * prev/next remain NULL; calling mk_list_del would dereference NULL. + */ + if (u->base._head.next != NULL && u->base._head.prev != NULL) { mk_list_del(&u->base._head); }
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src/flb_upstream.c(1 hunks)
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🔇 Additional comments (2)
src/flb_upstream.c (2)
683-687: Good fix: prevents segfault by only unlinking when the node is actually linked.This guard matches mk_list semantics where prev/next are NULL for non-linked nodes. It avoids dereferencing NULL inside mk_list_del when an upstream never made it into the list (e.g., failed during creation). No behavioral change for properly linked upstreams.
683-687: No other unguarded mk_list_del(&…->base._head) calls foundA repository-wide search for
mk_list_del(&…->base._head)returned exactly two sites:
- src/flb_upstream.c – now correctly guarded by
u->base._head.next != NULL && u->base._head.prev != NULL- src/flb_downstream.c – already protected via
mk_list_entry_orphan(&stream->base._head) == 0All other destructors invoke
flb_upstream_destroyunderif (ctx->u)checks. No additional unconditional deletions onbase._headexist.
edsiper
requested changes
Aug 20, 2025
Signed-off-by: Zhihong Lin <zhiholin@amazon.com>
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This fix prevents a segmentation fault in
flb_upstream_destroy()that occurs when destroying upstreams that failed during creation. The root cause is thatmk_list_del(&u->base._head)attempts to unlink from a list even when the upstream was never properly linked due to creation failures, causing the function to access NULL pointers in the list structure.This is because this line which links in the end but if any error occurs, the function returns NULL before calling the
mk_list_addfunction.Enter
[N/A]in the box, if an item is not applicable to your change.Testing
Before we can approve your change; please submit the following in a comment:
If this is a change to packaging of containers or native binaries then please confirm it works for all targets.
ok-package-testlabel to test for all targets (requires maintainer to do).Documentation
Backporting
Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.
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