[PATCH net v2 1/2] net: fman: move IRQ registration after init to prevent NULL deref and UAF

[ZhaoJinming <zhaojinming@uniontech.com>]

read_dts_node() registers shared interrupt handlers via
devm_request_irq() with fman as dev_id. Two bugs exist in the
current code:

1) Pre-init NULL dereference: at registration time fman is only
partially initialized -- kzalloc_obj() zero-initializes all fields,
so fman->cfg and fman->fpm_regs are NULL. The handlers check
is_init_done(fman->cfg) to guard against incomplete init, but
is_init_done(NULL) returns true (intended to mean cfg was freed
after successful init), so the guard is bypassed and fpm_regs is
dereferenced. If another device on the same shared IRQ line fires
during the window between devm_request_irq() and fman_init(), the
handler accesses NULL fpm_regs via ioread32be(), causing a crash.

2) Use-after-free on probe failure: fman is allocated with
kzalloc_obj() (not devm), so on error paths in read_dts_node()
(ioremap failure, of_platform_populate failure) and fman_config(),
kfree(fman) is called while the devm IRQ handlers remain
registered. The driver core's subsequent devres_release_all() frees
the IRQ handlers, but during the window between kfree(fman) and
devm_free_irq(), a shared-IRQ spurious firing will dereference
the already-freed fman.

A previous attempt to fix issue #1 with an irq_ready flag protected
by READ_ONCE()/WRITE_ONCE() is insufficient on weakly-ordered
architectures. READ_ONCE()/WRITE_ONCE() only prevent compiler
optimization; they do not provide the memory ordering guarantees
(e.g., smp_store_release/smp_load_acquire) needed to ensure that
writes to register pointers are visible to the IRQ handler before
it observes the flag as true.

Fix both issues by moving devm_request_irq() out of read_dts_node()
and into fman_probe(), after both fman_config() and fman_init()
have completed. This eliminates both race windows: by the time the
handlers are registered, all register pointers are initialized
(preventing the NULL dereference), and since fman is never freed
after this point, the use-after-free cannot occur either.

Add an 'irq' field to struct fman_dts_params so that the primary IRQ
number parsed in read_dts_node() is available to fman_probe().

This replaces the previous approach (irq_ready flag with READ_ONCE)
and also supersedes the separate UAF fix patch ("fsl_fman: fix
use-after-free on IRQF_SHARED handler after probe failure" v3),
as moving IRQ registration after init resolves both issues
in a single change.

v2:
- move devm_request_irq() to fman_probe() after init (replaces
  irq_ready + READ_ONCE approach from v1)
- supersede the separate UAF fix patch (v3), as this patch
  resolves both issues in a single change

Fixes: 414fd46e7762 ("fsl/fman: Add FMan support")
Link: https://lore.kernel.org/netdev/20260626162323.GE1310988@horms.kernel.org/
Signed-off-by: ZhaoJinming <zhaojinming@uniontech.com>
---
 drivers/net/ethernet/freescale/fman/fman.c | 52 +++++++++++++---------
 drivers/net/ethernet/freescale/fman/fman.h |  1 +
 2 files changed, 32 insertions(+), 21 deletions(-)

diff --git a/drivers/net/ethernet/freescale/fman/fman.c b/drivers/net/ethernet/freescale/fman/fman.c
index 299bab043175..6947f3bc7c87 100644
--- a/drivers/net/ethernet/freescale/fman/fman.c
+++ b/drivers/net/ethernet/freescale/fman/fman.c
@@ -2695,7 +2695,7 @@ static struct fman *read_dts_node(struct platform_device *of_dev)
 	void __iomem *base_addr;
 	struct resource *res;
 	u32 val, range[2];
-	int err, irq;
+	int err;
 	struct clk *clk;
 	u32 clk_rate;
 
@@ -2717,7 +2717,7 @@ static struct fman *read_dts_node(struct platform_device *of_dev)
 	err = platform_get_irq(of_dev, 0);
 	if (err < 0)
 		goto fman_node_put;
-	irq = err;
+	fman->dts_params.irq = err;
 
 	/* Get the FM error interrupt */
 	err = platform_get_irq(of_dev, 1);
@@ -2773,25 +2773,6 @@ static struct fman *read_dts_node(struct platform_device *of_dev)
 
 	of_node_put(muram_node);
 
-	err = devm_request_irq(&of_dev->dev, irq, fman_irq, IRQF_SHARED,
-			       "fman", fman);
-	if (err < 0) {
-		dev_err(&of_dev->dev, "%s: irq %d allocation failed (error = %d)\n",
-			__func__, irq, err);
-		goto fman_free;
-	}
-
-	if (fman->dts_params.err_irq != 0) {
-		err = devm_request_irq(&of_dev->dev, fman->dts_params.err_irq,
-				       fman_err_irq, IRQF_SHARED,
-				       "fman-err", fman);
-		if (err < 0) {
-			dev_err(&of_dev->dev, "%s: irq %d allocation failed (error = %d)\n",
-				__func__, fman->dts_params.err_irq, err);
-			goto fman_free;
-		}
-	}
-
 	base_addr = devm_platform_get_and_ioremap_resource(of_dev, 0, &res);
 	if (IS_ERR(base_addr)) {
 		err = PTR_ERR(base_addr);
@@ -2848,6 +2829,35 @@ static int fman_probe(struct platform_device *of_dev)
 		return -EINVAL;
 	}
 
+	/* Register IRQ handlers only after initialization is complete.
+	 * This prevents two issues:
+	 * 1) Pre-init NULL dereference: is_init_done(NULL) returns true,
+	 *    so a shared-IRQ spurious firing before fpm_regs is set would
+	 *    dereference NULL.
+	 * 2) Use-after-free on probe failure: fman was kzalloc'd (not devm),
+	 *    so on error paths kfree(fman) ran before devm_free_irq, leaving
+	 *    a window where the handler could fire with a freed dev_id.
+	 * By registering here, both problems are eliminated.
+	 */
+	err = devm_request_irq(dev, fman->dts_params.irq, fman_irq,
+			       IRQF_SHARED, "fman", fman);
+	if (err < 0) {
+		dev_err(dev, "%s: irq %d allocation failed (error = %d)\n",
+			__func__, fman->dts_params.irq, err);
+		return err;
+	}
+
+	if (fman->dts_params.err_irq != 0) {
+		err = devm_request_irq(dev, fman->dts_params.err_irq,
+				       fman_err_irq, IRQF_SHARED,
+				       "fman-err", fman);
+		if (err < 0) {
+			dev_err(dev, "%s: irq %d allocation failed (error = %d)\n",
+				__func__, fman->dts_params.err_irq, err);
+			return err;
+		}
+	}
+
 	if (fman->dts_params.err_irq == 0) {
 		fman_set_exception(fman, FMAN_EX_DMA_BUS_ERROR, false);
 		fman_set_exception(fman, FMAN_EX_DMA_READ_ECC, false);
diff --git a/drivers/net/ethernet/freescale/fman/fman.h b/drivers/net/ethernet/freescale/fman/fman.h
index 74eb62eba0d7..630d57c3144c 100644
--- a/drivers/net/ethernet/freescale/fman/fman.h
+++ b/drivers/net/ethernet/freescale/fman/fman.h
@@ -286,6 +286,7 @@ struct fman_dts_params {
 	struct resource *res;                   /* FMan memory resource */
 	u8 id;                                  /* FMan ID */
 
+	int irq;                                /* FMan IRQ */
 	int err_irq;                            /* FMan Error IRQ */
 
 	u16 clk_freq;                           /* FMan clock freq (In Mhz) */
-- 
2.20.1