fbnic: close fw_log race between users and teardown

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[ Upstream commit ee5492fd88 ]

Fixes a theoretical race on fw_log between the teardown path and fw_log
write functions.

fw_log is written inside fbnic_fw_log_write() and can be reached from
the mailbox handler fbnic_fw_msix_intr(), but fw_log is freed before
IRQ/MBX teardown during cleanup, resulting in a potential data race of
dereferencing a freed/null variable.

Possible Interleaving Scenario:
  CPU0: fbnic_fw_msix_intr() // Entry
          fbnic_fw_log_write()
            if (fbnic_fw_log_ready())   // true
            ... preempt ...
  CPU1: fbnic_remove() // Entry
          fbnic_fw_log_free()
            vfree(log->data_start);
            log->data_start = NULL;
  CPU0: continues, walks log->entries or writes to log->data_start

The initialization also has an incorrect order problem, as the fw_log
is currently allocated after MBX setup during initialization.
Fix the problems by adjusting the synchronization order to put
initialization in place before the mailbox is enabled, and not cleared
until after the mailbox has been disabled.

Fixes: ecc53b1b46 ("eth: fbnic: Enable firmware logging")
Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Link: https://patch.msgid.link/20260211191329.530886-1-dg573847474@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

...

This commit is contained in:

Chengfeng Ye 2026-02-11 19:13:29 +00:00 • committed by Greg Kroah-Hartman

parent 3795473398

commit 223cfef481

2 changed files with 12 additions and 10 deletions

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3

drivers/net/ethernet/meta/fbnic/fbnic_fw_log.c

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19

drivers/net/ethernet/meta/fbnic/fbnic_pci.c

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