From: duoming@zju.edu.cn To: "Michal Simek" <michal.simek@amd.com> Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, sboyd@kernel.org, mturquette@baylibre.com Subject: Re: [PATCH v2] clk: zynq: Prevent null pointer dereference caused by kmalloc failure Date: Thu, 29 Feb 2024 22:16:28 +0800 (GMT+08:00) [thread overview] Message-ID: <365f9a90.55b0.18df5394935.Coremail.duoming@zju.edu.cn> (raw) In-Reply-To: <2b274111-e65a-4b99-8f07-220324f1e214@amd.com> On Thu, 29 Feb 2024 13:45:54 +0100 Michal Simek wrote: > > The kmalloc() in zynq_clk_setup() will return null if the > > physical memory has run out. As a result, if we use snprintf > > to write data to the null address, the null pointer dereference > > bug will happen. > > > > This patch adds a stack variable to replace the kmalloc(). > > > > Fixes: 0ee52b157b8e ("clk: zynq: Add clock controller driver") > > Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> > > --- > > Changes in v2: > > - Use stack variable to replace kmalloc(). > > > > drivers/clk/zynq/clkc.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c > > index 7bdeaff2bfd..e4c4c9adf79 100644 > > --- a/drivers/clk/zynq/clkc.c > > +++ b/drivers/clk/zynq/clkc.c > > @@ -427,7 +427,7 @@ static void __init zynq_clk_setup(struct device_node *np) > > SLCR_GEM1_CLK_CTRL, 0, 0, &gem1clk_lock); > > > > tmp = strlen("mio_clk_00x"); > > - clk_name = kmalloc(tmp, GFP_KERNEL); > > + char clk_name[tmp]; > > I know that Stephen asked for it but variable with variable length in the middle > of code doesn't look good or useful. > I would allocate rather bigger array on stack with size bigger than max length > which will use it. The length of "mio_clk_00x" is 11 bytes, and the kernel will alloc 16 bytes to it. I use a local variable whose size is 16 bytes to replace it. The detail is shown below: diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c index 7bdeaff2bfd..81d530e3357 100644 --- a/drivers/clk/zynq/clkc.c +++ b/drivers/clk/zynq/clkc.c @@ -215,7 +215,7 @@ static void __init zynq_clk_setup(struct device_node *np) int i; u32 tmp; int ret; - char *clk_name; + char clk_name[16]; unsigned int fclk_enable = 0; const char *clk_output_name[clk_max]; const char *cpu_parents[4]; @@ -427,7 +427,6 @@ static void __init zynq_clk_setup(struct device_node *np) SLCR_GEM1_CLK_CTRL, 0, 0, &gem1clk_lock); tmp = strlen("mio_clk_00x"); - clk_name = kmalloc(tmp, GFP_KERNEL); for (i = 0; i < NUM_MIO_PINS; i++) { int idx; @@ -439,7 +438,6 @@ static void __init zynq_clk_setup(struct device_node *np) else can_mio_mux_parents[i] = dummy_nm; } - kfree(clk_name); clk_register_mux(NULL, "can_mux", periph_parents, 4, CLK_SET_RATE_NO_REPARENT, SLCR_CAN_CLK_CTRL, 4, 2, 0, &canclk_lock); Do you think the above is better? Best regards, Duoming Zhou
WARNING: multiple messages have this Message-ID (diff)
From: duoming@zju.edu.cn To: "Michal Simek" <michal.simek@amd.com> Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, sboyd@kernel.org, mturquette@baylibre.com Subject: Re: [PATCH v2] clk: zynq: Prevent null pointer dereference caused by kmalloc failure Date: Thu, 29 Feb 2024 22:16:28 +0800 (GMT+08:00) [thread overview] Message-ID: <365f9a90.55b0.18df5394935.Coremail.duoming@zju.edu.cn> (raw) In-Reply-To: <2b274111-e65a-4b99-8f07-220324f1e214@amd.com> On Thu, 29 Feb 2024 13:45:54 +0100 Michal Simek wrote: > > The kmalloc() in zynq_clk_setup() will return null if the > > physical memory has run out. As a result, if we use snprintf > > to write data to the null address, the null pointer dereference > > bug will happen. > > > > This patch adds a stack variable to replace the kmalloc(). > > > > Fixes: 0ee52b157b8e ("clk: zynq: Add clock controller driver") > > Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> > > --- > > Changes in v2: > > - Use stack variable to replace kmalloc(). > > > > drivers/clk/zynq/clkc.c | 3 +-- > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c > > index 7bdeaff2bfd..e4c4c9adf79 100644 > > --- a/drivers/clk/zynq/clkc.c > > +++ b/drivers/clk/zynq/clkc.c > > @@ -427,7 +427,7 @@ static void __init zynq_clk_setup(struct device_node *np) > > SLCR_GEM1_CLK_CTRL, 0, 0, &gem1clk_lock); > > > > tmp = strlen("mio_clk_00x"); > > - clk_name = kmalloc(tmp, GFP_KERNEL); > > + char clk_name[tmp]; > > I know that Stephen asked for it but variable with variable length in the middle > of code doesn't look good or useful. > I would allocate rather bigger array on stack with size bigger than max length > which will use it. The length of "mio_clk_00x" is 11 bytes, and the kernel will alloc 16 bytes to it. I use a local variable whose size is 16 bytes to replace it. The detail is shown below: diff --git a/drivers/clk/zynq/clkc.c b/drivers/clk/zynq/clkc.c index 7bdeaff2bfd..81d530e3357 100644 --- a/drivers/clk/zynq/clkc.c +++ b/drivers/clk/zynq/clkc.c @@ -215,7 +215,7 @@ static void __init zynq_clk_setup(struct device_node *np) int i; u32 tmp; int ret; - char *clk_name; + char clk_name[16]; unsigned int fclk_enable = 0; const char *clk_output_name[clk_max]; const char *cpu_parents[4]; @@ -427,7 +427,6 @@ static void __init zynq_clk_setup(struct device_node *np) SLCR_GEM1_CLK_CTRL, 0, 0, &gem1clk_lock); tmp = strlen("mio_clk_00x"); - clk_name = kmalloc(tmp, GFP_KERNEL); for (i = 0; i < NUM_MIO_PINS; i++) { int idx; @@ -439,7 +438,6 @@ static void __init zynq_clk_setup(struct device_node *np) else can_mio_mux_parents[i] = dummy_nm; } - kfree(clk_name); clk_register_mux(NULL, "can_mux", periph_parents, 4, CLK_SET_RATE_NO_REPARENT, SLCR_CAN_CLK_CTRL, 4, 2, 0, &canclk_lock); Do you think the above is better? Best regards, Duoming Zhou _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2024-02-29 14:16 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-02-29 12:22 [PATCH v2] clk: zynq: Prevent null pointer dereference caused by kmalloc failure Duoming Zhou 2024-02-29 12:22 ` Duoming Zhou 2024-02-29 12:45 ` Michal Simek 2024-02-29 12:45 ` Michal Simek 2024-02-29 14:16 ` duoming [this message] 2024-02-29 14:16 ` duoming 2024-03-01 1:22 ` Stephen Boyd 2024-03-01 1:22 ` Stephen Boyd 2024-03-01 1:21 ` Stephen Boyd 2024-03-01 1:21 ` Stephen Boyd 2024-03-01 7:02 ` Michal Simek 2024-03-01 7:02 ` Michal Simek
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