[PATCH] mtd: core: Fix freeing of otp_info buffer

[PATCH] mtd: core: Fix freeing of otp_info buffer

[Jon Hunter]

Commit 4b361cfa8624 ("mtd: core: add OTP nvmem provider support") is
causing the following panic ...

 ------------[ cut here ]------------
 kernel BUG at /local/workdir/tegra/linux_next/kernel/mm/slab.c:2730!
 Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
 Modules linked in:
 CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.13.0-rc2-next-20210518 #1
 Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
 PC is at ___cache_free+0x3f8/0x51c
 ...
 [<c029bb1c>] (___cache_free) from [<c029c658>] (kfree+0xac/0x1bc)
 [<c029c658>] (kfree) from [<c06da094>] (mtd_otp_size+0xc4/0x108)
 [<c06da094>] (mtd_otp_size) from [<c06dc864>] (mtd_device_parse_register+0xe4/0x2b4)
 [<c06dc864>] (mtd_device_parse_register) from [<c06e3ccc>] (spi_nor_probe+0x210/0x2c0)
 [<c06e3ccc>] (spi_nor_probe) from [<c06e9578>] (spi_probe+0x88/0xac)
 [<c06e9578>] (spi_probe) from [<c066891c>] (really_probe+0x214/0x3a4)
 [<c066891c>] (really_probe) from [<c0668b14>] (driver_probe_device+0x68/0xc0)
 [<c0668b14>] (driver_probe_device) from [<c0666cf8>] (bus_for_each_drv+0x5c/0xbc)
 [<c0666cf8>] (bus_for_each_drv) from [<c0668694>] (__device_attach+0xe4/0x150)
 [<c0668694>] (__device_attach) from [<c06679e0>] (bus_probe_device+0x84/0x8c)
 [<c06679e0>] (bus_probe_device) from [<c06657f8>] (device_add+0x48c/0x868)
 [<c06657f8>] (device_add) from [<c06eb784>] (spi_add_device+0xa0/0x168)
 [<c06eb784>] (spi_add_device) from [<c06ec9a8>] (spi_register_controller+0x8b8/0xb38)
 [<c06ec9a8>] (spi_register_controller) from [<c06ecc3c>] (devm_spi_register_controller+0x14/0x50)
 [<c06ecc3c>] (devm_spi_register_controller) from [<c06f0510>] (tegra_spi_probe+0x33c/0x450)
 [<c06f0510>] (tegra_spi_probe) from [<c066abec>] (platform_probe+0x5c/0xb8)
 [<c066abec>] (platform_probe) from [<c066891c>] (really_probe+0x214/0x3a4)
 [<c066891c>] (really_probe) from [<c0668b14>] (driver_probe_device+0x68/0xc0)
 [<c0668b14>] (driver_probe_device) from [<c0668e30>] (device_driver_attach+0x58/0x60)
 [<c0668e30>] (device_driver_attach) from [<c0668eb8>] (__driver_attach+0x80/0xc8)
 [<c0668eb8>] (__driver_attach) from [<c0666c48>] (bus_for_each_dev+0x78/0xb8)
 [<c0666c48>] (bus_for_each_dev) from [<c0667c44>] (bus_add_driver+0x164/0x1e8)
 [<c0667c44>] (bus_add_driver) from [<c066997c>] (driver_register+0x7c/0x114)
 [<c066997c>] (driver_register) from [<c010223c>] (do_one_initcall+0x50/0x2b0)
 [<c010223c>] (do_one_initcall) from [<c11011f0>] (kernel_init_freeable+0x1a8/0x1fc)
 [<c11011f0>] (kernel_init_freeable) from [<c0c09190>] (kernel_init+0x8/0x118)
 [<c0c09190>] (kernel_init) from [<c01001b0>] (ret_from_fork+0x14/0x24)
 ...
 ---[ end trace 0f652dd222de75d7 ]---

In the function mtd_otp_size() a buffer is allocated by calling
kmalloc() and a pointer to the buffer is stored in a variable 'info'.
The pointer 'info' may then be incremented depending on the length
returned from mtd_get_user/fact_prot_info(). If 'info' is incremented,
when kfree() is called to free the buffer the above panic occurs because
we are no longer passing the original address of the buffer allocated.
Fix this by indexing through the buffer allocated to avoid incrementing
the pointer.

Fixes: 4b361cfa8624 ("mtd: core: add OTP nvmem provider support")
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
---
 drivers/mtd/mtdcore.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 3ae261661eea..ffa46ccea0cf 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -792,10 +792,8 @@ static ssize_t mtd_otp_size(struct mtd_info *mtd, bool is_user)
 	if (ret)
 		goto err;
 
-	for (i = 0; i < retlen / sizeof(*info); i++) {
-		size += info->length;
-		info++;
-	}
+	for (i = 0; i < retlen / sizeof(*info); i++)
+		size += info[i].length;
 
 	kfree(info);
 	return size;
-- 
2.7.4

Re: [PATCH] mtd: core: Fix freeing of otp_info buffer

[Michael Walle]

Am 2021-05-18 20:55, schrieb Jon Hunter:
> Commit 4b361cfa8624 ("mtd: core: add OTP nvmem provider support") is
> causing the following panic ...
> 
>  ------------[ cut here ]------------
>  kernel BUG at /local/workdir/tegra/linux_next/kernel/mm/slab.c:2730!
>  Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>  Modules linked in:
>  CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.13.0-rc2-next-20210518 #1
>  Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
>  PC is at ___cache_free+0x3f8/0x51c
>  ...
>  [<c029bb1c>] (___cache_free) from [<c029c658>] (kfree+0xac/0x1bc)
>  [<c029c658>] (kfree) from [<c06da094>] (mtd_otp_size+0xc4/0x108)
>  [<c06da094>] (mtd_otp_size) from [<c06dc864>]
> (mtd_device_parse_register+0xe4/0x2b4)
>  [<c06dc864>] (mtd_device_parse_register) from [<c06e3ccc>]
> (spi_nor_probe+0x210/0x2c0)
>  [<c06e3ccc>] (spi_nor_probe) from [<c06e9578>] (spi_probe+0x88/0xac)
>  [<c06e9578>] (spi_probe) from [<c066891c>] (really_probe+0x214/0x3a4)
>  [<c066891c>] (really_probe) from [<c0668b14>] 
> (driver_probe_device+0x68/0xc0)
>  [<c0668b14>] (driver_probe_device) from [<c0666cf8>]
> (bus_for_each_drv+0x5c/0xbc)
>  [<c0666cf8>] (bus_for_each_drv) from [<c0668694>] 
> (__device_attach+0xe4/0x150)
>  [<c0668694>] (__device_attach) from [<c06679e0>] 
> (bus_probe_device+0x84/0x8c)
>  [<c06679e0>] (bus_probe_device) from [<c06657f8>] 
> (device_add+0x48c/0x868)
>  [<c06657f8>] (device_add) from [<c06eb784>] 
> (spi_add_device+0xa0/0x168)
>  [<c06eb784>] (spi_add_device) from [<c06ec9a8>]
> (spi_register_controller+0x8b8/0xb38)
>  [<c06ec9a8>] (spi_register_controller) from [<c06ecc3c>]
> (devm_spi_register_controller+0x14/0x50)
>  [<c06ecc3c>] (devm_spi_register_controller) from [<c06f0510>]
> (tegra_spi_probe+0x33c/0x450)
>  [<c06f0510>] (tegra_spi_probe) from [<c066abec>] 
> (platform_probe+0x5c/0xb8)
>  [<c066abec>] (platform_probe) from [<c066891c>] 
> (really_probe+0x214/0x3a4)
>  [<c066891c>] (really_probe) from [<c0668b14>] 
> (driver_probe_device+0x68/0xc0)
>  [<c0668b14>] (driver_probe_device) from [<c0668e30>]
> (device_driver_attach+0x58/0x60)
>  [<c0668e30>] (device_driver_attach) from [<c0668eb8>]
> (__driver_attach+0x80/0xc8)
>  [<c0668eb8>] (__driver_attach) from [<c0666c48>] 
> (bus_for_each_dev+0x78/0xb8)
>  [<c0666c48>] (bus_for_each_dev) from [<c0667c44>] 
> (bus_add_driver+0x164/0x1e8)
>  [<c0667c44>] (bus_add_driver) from [<c066997c>] 
> (driver_register+0x7c/0x114)
>  [<c066997c>] (driver_register) from [<c010223c>] 
> (do_one_initcall+0x50/0x2b0)
>  [<c010223c>] (do_one_initcall) from [<c11011f0>]
> (kernel_init_freeable+0x1a8/0x1fc)
>  [<c11011f0>] (kernel_init_freeable) from [<c0c09190>] 
> (kernel_init+0x8/0x118)
>  [<c0c09190>] (kernel_init) from [<c01001b0>] (ret_from_fork+0x14/0x24)
>  ...
>  ---[ end trace 0f652dd222de75d7 ]---
> 
> In the function mtd_otp_size() a buffer is allocated by calling
> kmalloc() and a pointer to the buffer is stored in a variable 'info'.
> The pointer 'info' may then be incremented depending on the length
> returned from mtd_get_user/fact_prot_info(). If 'info' is incremented,
> when kfree() is called to free the buffer the above panic occurs 
> because
> we are no longer passing the original address of the buffer allocated.
> Fix this by indexing through the buffer allocated to avoid incrementing
> the pointer.
> 
> Fixes: 4b361cfa8624 ("mtd: core: add OTP nvmem provider support")
> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>

uhm.. yes of course. Two fixes for this function. Not my best day :/

I'm wondering why CONFIG_SLUB_DEBUG_ON doesn't catch this, whereas
slub_debug=f (or fzpu) as commandline parameter works as expected.

Reviewed-by: Michael Walle <michael@walle.cc>

Thanks,
-michael

Re: [PATCH] mtd: core: Fix freeing of otp_info buffer

[Miquel Raynal]

On Tue, 2021-05-18 at 18:55:03 UTC, Jon Hunter wrote:
> Commit 4b361cfa8624 ("mtd: core: add OTP nvmem provider support") is
> causing the following panic ...
> 
>  ------------[ cut here ]------------
>  kernel BUG at /local/workdir/tegra/linux_next/kernel/mm/slab.c:2730!
>  Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>  Modules linked in:
>  CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.13.0-rc2-next-20210518 #1
>  Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
>  PC is at ___cache_free+0x3f8/0x51c
>  ...
>  [<c029bb1c>] (___cache_free) from [<c029c658>] (kfree+0xac/0x1bc)
>  [<c029c658>] (kfree) from [<c06da094>] (mtd_otp_size+0xc4/0x108)
>  [<c06da094>] (mtd_otp_size) from [<c06dc864>] (mtd_device_parse_register+0xe4/0x2b4)
>  [<c06dc864>] (mtd_device_parse_register) from [<c06e3ccc>] (spi_nor_probe+0x210/0x2c0)
>  [<c06e3ccc>] (spi_nor_probe) from [<c06e9578>] (spi_probe+0x88/0xac)
>  [<c06e9578>] (spi_probe) from [<c066891c>] (really_probe+0x214/0x3a4)
>  [<c066891c>] (really_probe) from [<c0668b14>] (driver_probe_device+0x68/0xc0)
>  [<c0668b14>] (driver_probe_device) from [<c0666cf8>] (bus_for_each_drv+0x5c/0xbc)
>  [<c0666cf8>] (bus_for_each_drv) from [<c0668694>] (__device_attach+0xe4/0x150)
>  [<c0668694>] (__device_attach) from [<c06679e0>] (bus_probe_device+0x84/0x8c)
>  [<c06679e0>] (bus_probe_device) from [<c06657f8>] (device_add+0x48c/0x868)
>  [<c06657f8>] (device_add) from [<c06eb784>] (spi_add_device+0xa0/0x168)
>  [<c06eb784>] (spi_add_device) from [<c06ec9a8>] (spi_register_controller+0x8b8/0xb38)
>  [<c06ec9a8>] (spi_register_controller) from [<c06ecc3c>] (devm_spi_register_controller+0x14/0x50)
>  [<c06ecc3c>] (devm_spi_register_controller) from [<c06f0510>] (tegra_spi_probe+0x33c/0x450)
>  [<c06f0510>] (tegra_spi_probe) from [<c066abec>] (platform_probe+0x5c/0xb8)
>  [<c066abec>] (platform_probe) from [<c066891c>] (really_probe+0x214/0x3a4)
>  [<c066891c>] (really_probe) from [<c0668b14>] (driver_probe_device+0x68/0xc0)
>  [<c0668b14>] (driver_probe_device) from [<c0668e30>] (device_driver_attach+0x58/0x60)
>  [<c0668e30>] (device_driver_attach) from [<c0668eb8>] (__driver_attach+0x80/0xc8)
>  [<c0668eb8>] (__driver_attach) from [<c0666c48>] (bus_for_each_dev+0x78/0xb8)
>  [<c0666c48>] (bus_for_each_dev) from [<c0667c44>] (bus_add_driver+0x164/0x1e8)
>  [<c0667c44>] (bus_add_driver) from [<c066997c>] (driver_register+0x7c/0x114)
>  [<c066997c>] (driver_register) from [<c010223c>] (do_one_initcall+0x50/0x2b0)
>  [<c010223c>] (do_one_initcall) from [<c11011f0>] (kernel_init_freeable+0x1a8/0x1fc)
>  [<c11011f0>] (kernel_init_freeable) from [<c0c09190>] (kernel_init+0x8/0x118)
>  [<c0c09190>] (kernel_init) from [<c01001b0>] (ret_from_fork+0x14/0x24)
>  ...
>  ---[ end trace 0f652dd222de75d7 ]---
> 
> In the function mtd_otp_size() a buffer is allocated by calling
> kmalloc() and a pointer to the buffer is stored in a variable 'info'.
> The pointer 'info' may then be incremented depending on the length
> returned from mtd_get_user/fact_prot_info(). If 'info' is incremented,
> when kfree() is called to free the buffer the above panic occurs because
> we are no longer passing the original address of the buffer allocated.
> Fix this by indexing through the buffer allocated to avoid incrementing
> the pointer.
> 
> Fixes: 4b361cfa8624 ("mtd: core: add OTP nvmem provider support")
> Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
> Reviewed-by: Michael Walle <michael@walle.cc>

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux.git mtd/next, thanks.

Miquel