kmemleak observed after system boots up

bug report Applied Yi Zhang 3 participants 5 messages Apr 3, 2024 – May 3, 2024

Subsystems (2)

Stable branch fs-verity: read-only file-based authenticity protection

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Yi Zhang

author

2024-04-03 02:20 UTC #0 lore raw

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)

Signature · 2 lines

Best Regards,
  Yi Zhang

Yi Zhang

author

2024-04-29 01:47 UTC #1 lore raw

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

Quoted 44 lines · 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

Signature · 2 lines

Best Regards,
  Yi Zhang

Eric Biggers

maintainer

2024-05-01 02:54 UTC #2 lore raw

PATCH 1/1 fsverity: use register_sysctl_init() to avoid kmemleak warning

From: Eric Biggers <[email protected]>

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 <[email protected]>

Closes https://lore.kernel.org/r/CAHj4cs8DTSvR698UE040rs_pX1k-WVe7aR6N2OoXXuhXJPDC-w@mail.gmail.com open here

Cc [email protected]

Signed-off-by Eric Biggers <[email protected]>

---
 fs/verity/init.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

fs/verity/init.c +1 -6

index cb2c9aac61ed..f440f0e61e3e 100644
@@ -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

Signature · 1 line

2.45.0

Joel Granados

Reviewed-by on v1 1/1

2024-05-03 14:01 UTC #3 lore raw

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

Quoted 53 lines · Eric Biggers

From: Eric Biggers <[email protected]>
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 <[email protected]>
Closes https://lore.kernel.org/r/CAHj4cs8DTSvR698UE040rs_pX1k-WVe7aR6N2OoXXuhXJPDC-w@mail.gmail.com open here
Cc [email protected]
Signed-off-by Eric Biggers <[email protected]>
---
 fs/verity/init.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)
fs/verity/init.c +1 -6
index cb2c9aac61ed..f440f0e61e3e 100644
@@ -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)
 {
 }

Quoted 4 lines

base-commit: 18daea77cca626f590fb140fc11e3a43c5d41354
Signature · 1 line
2.45.0

LGTM

Reviewed-by Joel Granados <[email protected]>

Signature · 1 line

Joel Granados

Eric Biggers

maintainer Applied

2024-05-03 15:30 UTC #4 lore raw

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

In reply to Eric Biggers

Quoted 11 lines · Eric Biggers

From: Eric Biggers <[email protected]>
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().

Quoted 4 lines

Reported-by Yi Zhang <[email protected]>
Closes https://lore.kernel.org/r/CAHj4cs8DTSvR698UE040rs_pX1k-WVe7aR6N2OoXXuhXJPDC-w@mail.gmail.com open here
Cc [email protected]
Signed-off-by Eric Biggers <[email protected]>

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

- Eric