[bug report] kmemleak observed after system boots up

[bug report] kmemleak observed after system boots up

[Yi Zhang]

Hello
I found this kmemleak after system boots up on the latest
linux-block/for-next, please help check it and let me know if you need
any testing/info about it, thanks.

# dmesg | grep kmemleak
[  474.750916] kmemleak: 1 new suspected memory leaks (see
/sys/kernel/debug/kmemleak)

# cat /sys/kernel/debug/kmemleak
unreferenced object 0xffff88824046a580 (size 96):
  comm "swapper/0", pid 1, jiffies 4294727564
  hex dump (first 32 bytes):
    a0 c2 0d 9b ff ff ff ff 00 00 00 00 00 00 00 00  ................
    01 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc e7670296):
    [<ffffffff9412657c>] __kmalloc+0x37c/0x480
    [<ffffffff944cfbf8>] __register_sysctl_table+0x58/0x450
    [<ffffffff98680079>] fsverity_init+0x29/0x50
    [<ffffffff9360371e>] do_one_initcall+0xfe/0x5a0
    [<ffffffff985b70d8>] do_initcalls+0x138/0x1d0
    [<ffffffff985b7aac>] kernel_init_freeable+0x8bc/0xbe0
    [<ffffffff95dba94b>] kernel_init+0x1b/0x1e0
    [<ffffffff936a804d>] ret_from_fork+0x2d/0x70
    [<ffffffff93606e4a>] ret_from_fork_asm+0x1a/0x30

(gdb) l *(fsverity_init+0x29)
0xffffffff86080079 is in fsverity_init (fs/verity/init.c:33).
28
29 static void __init fsverity_init_sysctl(void)
30 {
31 fsverity_sysctl_header = register_sysctl("fs/verity",
32 fsverity_sysctl_table);
33 if (!fsverity_sysctl_header)
34 panic("fsverity sysctl registration failed");
35 }
36 #else /* CONFIG_SYSCTL */
37 static inline void fsverity_init_sysctl(void)


-- 
Best Regards,
  Yi Zhang

Re: [bug report] kmemleak observed after system boots up

[Yi Zhang]

Hi Eric
Seems this issue was introduced from 6.6-rc1, do you have a chance to
check it, thanks.


On Wed, Apr 3, 2024 at 10:20 AM Yi Zhang <yi.zhang@redhat.com> wrote:
>
> Hello
> I found this kmemleak after system boots up on the latest
> linux-block/for-next, please help check it and let me know if you need
> any testing/info about it, thanks.
>
> # dmesg | grep kmemleak
> [  474.750916] kmemleak: 1 new suspected memory leaks (see
> /sys/kernel/debug/kmemleak)
>
> # cat /sys/kernel/debug/kmemleak
> unreferenced object 0xffff88824046a580 (size 96):
>   comm "swapper/0", pid 1, jiffies 4294727564
>   hex dump (first 32 bytes):
>     a0 c2 0d 9b ff ff ff ff 00 00 00 00 00 00 00 00  ................
>     01 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace (crc e7670296):
>     [<ffffffff9412657c>] __kmalloc+0x37c/0x480
>     [<ffffffff944cfbf8>] __register_sysctl_table+0x58/0x450
>     [<ffffffff98680079>] fsverity_init+0x29/0x50
>     [<ffffffff9360371e>] do_one_initcall+0xfe/0x5a0
>     [<ffffffff985b70d8>] do_initcalls+0x138/0x1d0
>     [<ffffffff985b7aac>] kernel_init_freeable+0x8bc/0xbe0
>     [<ffffffff95dba94b>] kernel_init+0x1b/0x1e0
>     [<ffffffff936a804d>] ret_from_fork+0x2d/0x70
>     [<ffffffff93606e4a>] ret_from_fork_asm+0x1a/0x30
>
> (gdb) l *(fsverity_init+0x29)
> 0xffffffff86080079 is in fsverity_init (fs/verity/init.c:33).
> 28
> 29 static void __init fsverity_init_sysctl(void)
> 30 {
> 31 fsverity_sysctl_header = register_sysctl("fs/verity",
> 32 fsverity_sysctl_table);
> 33 if (!fsverity_sysctl_header)
> 34 panic("fsverity sysctl registration failed");
> 35 }
> 36 #else /* CONFIG_SYSCTL */
> 37 static inline void fsverity_init_sysctl(void)
>
>
> --
> Best Regards,
>   Yi Zhang



-- 
Best Regards,
  Yi Zhang

[PATCH] fsverity: use register_sysctl_init() to avoid kmemleak warning

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

Since the fsverity sysctl registration runs as a builtin initcall, there
is no corresponding sysctl deregistration and the resulting struct
ctl_table_header is not used.  This can cause a kmemleak warning just
after the system boots up.  (A pointer to the ctl_table_header is stored
in the fsverity_sysctl_header static variable, which kmemleak should
detect; however, the compiler can optimize out that variable.)  Avoid
the kmemleak warning by using register_sysctl_init() which is intended
for use by builtin initcalls and uses kmemleak_not_leak().

Reported-by: Yi Zhang <yi.zhang@redhat.com>
Closes: https://lore.kernel.org/r/CAHj4cs8DTSvR698UE040rs_pX1k-WVe7aR6N2OoXXuhXJPDC-w@mail.gmail.com
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/verity/init.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/fs/verity/init.c b/fs/verity/init.c
index cb2c9aac61ed..f440f0e61e3e 100644
--- a/fs/verity/init.c
+++ b/fs/verity/init.c
@@ -8,12 +8,10 @@
 #include "fsverity_private.h"
 
 #include <linux/ratelimit.h>
 
 #ifdef CONFIG_SYSCTL
-static struct ctl_table_header *fsverity_sysctl_header;
-
 static struct ctl_table fsverity_sysctl_table[] = {
 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
 	{
 		.procname       = "require_signatures",
 		.data           = &fsverity_require_signatures,
@@ -26,14 +24,11 @@ static struct ctl_table fsverity_sysctl_table[] = {
 #endif
 };
 
 static void __init fsverity_init_sysctl(void)
 {
-	fsverity_sysctl_header = register_sysctl("fs/verity",
-						 fsverity_sysctl_table);
-	if (!fsverity_sysctl_header)
-		panic("fsverity sysctl registration failed");
+	register_sysctl_init("fs/verity", fsverity_sysctl_table);
 }
 #else /* CONFIG_SYSCTL */
 static inline void fsverity_init_sysctl(void)
 {
 }

base-commit: 18daea77cca626f590fb140fc11e3a43c5d41354
-- 
2.45.0

Re: [PATCH] fsverity: use register_sysctl_init() to avoid kmemleak warning

[Joel Granados]

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On Tue, Apr 30, 2024 at 07:53:31PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Since the fsverity sysctl registration runs as a builtin initcall, there
> is no corresponding sysctl deregistration and the resulting struct
> ctl_table_header is not used.  This can cause a kmemleak warning just
> after the system boots up.  (A pointer to the ctl_table_header is stored
> in the fsverity_sysctl_header static variable, which kmemleak should
> detect; however, the compiler can optimize out that variable.)  Avoid
> the kmemleak warning by using register_sysctl_init() which is intended
> for use by builtin initcalls and uses kmemleak_not_leak().
> 
> Reported-by: Yi Zhang <yi.zhang@redhat.com>
> Closes: https://lore.kernel.org/r/CAHj4cs8DTSvR698UE040rs_pX1k-WVe7aR6N2OoXXuhXJPDC-w@mail.gmail.com
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  fs/verity/init.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/fs/verity/init.c b/fs/verity/init.c
> index cb2c9aac61ed..f440f0e61e3e 100644
> --- a/fs/verity/init.c
> +++ b/fs/verity/init.c
> @@ -8,12 +8,10 @@
>  #include "fsverity_private.h"
>  
>  #include <linux/ratelimit.h>
>  
>  #ifdef CONFIG_SYSCTL
> -static struct ctl_table_header *fsverity_sysctl_header;
> -
>  static struct ctl_table fsverity_sysctl_table[] = {
>  #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
>  	{
>  		.procname       = "require_signatures",
>  		.data           = &fsverity_require_signatures,
> @@ -26,14 +24,11 @@ static struct ctl_table fsverity_sysctl_table[] = {
>  #endif
>  };
>  
>  static void __init fsverity_init_sysctl(void)
>  {
> -	fsverity_sysctl_header = register_sysctl("fs/verity",
> -						 fsverity_sysctl_table);
> -	if (!fsverity_sysctl_header)
> -		panic("fsverity sysctl registration failed");
> +	register_sysctl_init("fs/verity", fsverity_sysctl_table);
>  }
>  #else /* CONFIG_SYSCTL */
>  static inline void fsverity_init_sysctl(void)
>  {
>  }
> 
> base-commit: 18daea77cca626f590fb140fc11e3a43c5d41354
> -- 
> 2.45.0
> 
LGTM

Reviewed-by: Joel Granados <j.granados@samsung.com>

-- 

Joel Granados

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Re: [PATCH] fsverity: use register_sysctl_init() to avoid kmemleak warning

[Eric Biggers]

On Tue, Apr 30, 2024 at 07:53:31PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> Since the fsverity sysctl registration runs as a builtin initcall, there
> is no corresponding sysctl deregistration and the resulting struct
> ctl_table_header is not used.  This can cause a kmemleak warning just
> after the system boots up.  (A pointer to the ctl_table_header is stored
> in the fsverity_sysctl_header static variable, which kmemleak should
> detect; however, the compiler can optimize out that variable.)  Avoid
> the kmemleak warning by using register_sysctl_init() which is intended
> for use by builtin initcalls and uses kmemleak_not_leak().
> 
> Reported-by: Yi Zhang <yi.zhang@redhat.com>
> Closes: https://lore.kernel.org/r/CAHj4cs8DTSvR698UE040rs_pX1k-WVe7aR6N2OoXXuhXJPDC-w@mail.gmail.com
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@google.com>

Applied to https://git.kernel.org/pub/scm/fs/fsverity/linux.git/log/?h=for-next

- Eric