linux-kernel - [PATCH AUTOSEL 6.12 169/486] PCI: endpoint: pci-epf-test: Fix double free that causes kernel to oops

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Message-Id: <20250505223922.2682012-169-sashal@kernel.org>
Date: Mon,  5 May 2025 18:34:05 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Christian Bruel <christian.bruel@...s.st.com>,
	Niklas Cassel <cassel@...nel.org>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	kw@...ux.com,
	bhelgaas@...gle.com,
	Frank.Li@....com,
	dlemoal@...nel.org,
	jiangwang@...inos.cn,
	linux-pci@...r.kernel.org
Subject: [PATCH AUTOSEL 6.12 169/486] PCI: endpoint: pci-epf-test: Fix double free that causes kernel to oops

From: Christian Bruel <christian.bruel@...s.st.com>

[ Upstream commit 934e9d137d937706004c325fa1474f9e3f1ba10a ]

Fix a kernel oops found while testing the stm32_pcie Endpoint driver
with handling of PERST# deassertion:

During EP initialization, pci_epf_test_alloc_space() allocates all BARs,
which are further freed if epc_set_bar() fails (for instance, due to no
free inbound window).

However, when pci_epc_set_bar() fails, the error path:

  pci_epc_set_bar() ->
    pci_epf_free_space()

does not clear the previous assignment to epf_test->reg[bar].

Then, if the host reboots, the PERST# deassertion restarts the BAR
allocation sequence with the same allocation failure (no free inbound
window), creating a double free situation since epf_test->reg[bar] was
deallocated and is still non-NULL.

Thus, make sure that pci_epf_alloc_space() and pci_epf_free_space()
invocations are symmetric, and as such, set epf_test->reg[bar] to NULL
when memory is freed.

Reviewed-by: Niklas Cassel <cassel@...nel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Signed-off-by: Christian Bruel <christian.bruel@...s.st.com>
Link: https://lore.kernel.org/r/20250124123043.96112-1-christian.bruel@foss.st.com
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/pci/endpoint/functions/pci-epf-test.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index 14b4c68ab4e1a..21aa3709e2577 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -703,6 +703,7 @@ static int pci_epf_test_set_bar(struct pci_epf *epf)
 		if (ret) {
 			pci_epf_free_space(epf, epf_test->reg[bar], bar,
 					   PRIMARY_INTERFACE);
+			epf_test->reg[bar] = NULL;
 			dev_err(dev, "Failed to set BAR%d\n", bar);
 			if (bar == test_reg_bar)
 				return ret;
@@ -878,6 +879,7 @@ static void pci_epf_test_free_space(struct pci_epf *epf)
 
 		pci_epf_free_space(epf, epf_test->reg[bar], bar,
 				   PRIMARY_INTERFACE);
+		epf_test->reg[bar] = NULL;
 	}
 }
 
-- 
2.39.5