Re: INFO: REPRODUCED: memory leak in gpio device in 6.2-rc6

[Andy Shevchenko]

On Wed, Feb 08, 2023 at 08:55:24PM +0100, Mirsad Goran Todorovac wrote:
> On 31. 01. 2023. 10:36, Mirsad Goran Todorovac wrote:
> > I came across this memory leak apparently in the GPIO device driver.
> > It is still present in 6.2-rc6 release candidate kernel (just ran kselftest).
> > 
> > This is a vanilla Torvalds tree kernel with MGLRU and KMEMLEAK (obviously)
> > enabled.
> > 
> > If you think this bug is significant, I can attempt the bug bisect in the
> > environment that triggered it (Lenovo LENOVO_MT_10TX_BU_Lenovo_FM_V530S-07ICB)
> > with BIOS M22KT49A from 11/10/2022 and AlmaLinux 8.7.
> > 
> > Here is the /sys/kernel/debug/kmemleak output:
> > 
> > unreferenced object 0xffff9e67ad71f160 (size 32):
> >   comm "gpio-sim.sh", pid 208926, jiffies 4372229685 (age 2101.564s)
> >   hex dump (first 32 bytes):
> >     67 70 69 6f 2d 73 69 6d 2e 30 2d 6e 6f 64 65 30  gpio-sim.0-node0
> >     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >   backtrace:
> >     [<0000000098bf3d1b>] slab_post_alloc_hook+0x91/0x320
> >     [<00000000da3205c5>] __kmem_cache_alloc_node+0x1bf/0x2b0
> >     [<00000000aa51a58a>] __kmalloc_node_track_caller+0x55/0x140
> >     [<00000000bd682ecc>] kvasprintf+0x6b/0xd0
> >     [<00000000a3431d55>] kasprintf+0x4e/0x70
> >     [<00000000f52d2629>] gpio_sim_device_config_live_store+0x401/0x59d [gpio_sim]
> >     [<00000000673fc6df>] configfs_write_iter+0xcc/0x130
> >     [<000000001d5d0829>] vfs_write+0x2b4/0x3d0
> >     [<00000000d2336251>] ksys_write+0x61/0xe0
> >     [<00000000f7015bb1>] __x64_sys_write+0x1a/0x20
> >     [<000000008ac743d2>] do_syscall_64+0x58/0x80
> >     [<000000004d7b7d50>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > [root@pc-mtodorov marvin]#
> 
> The new development on the bug is that it probably requires some superuser privileges
> or some capability to be exploited, for it requires access to configfs,
> but it was reproduced on different hardware as well.
> 
> The minimum reproducing script is attached, with its output log.
> 
> From the testing "age" of the unreferenced object I assume that it is allocated earlier
> in a part of script I am unable to locate or specify, but orphaned at the end of the script.
> 
> root@/home/user/kernel_bugs/gpio-sim# time ./gpio-reproduce-min.sh
> 2.14. Lines can be hogged
> Scanning stage 2.14.7 ... done.
> Sleeping 60 seconds ... done.
> Stage 2.14.7 clean.
> Rescanning stage 2.14.7 ... done.
> Sleeping 60 seconds ... done.
> unreferenced object 0xffff9593b9d16bc0 (size 32):
>   comm "gpio-reproduce-", pid 7594, jiffies 4295865460 (age 136.184s)
>   hex dump (first 32 bytes):
>     67 70 69 6f 2d 73 69 6d 2e 30 2d 6e 6f 64 65 30  gpio-sim.0-node0
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<00000000fe76444b>] __kmem_cache_alloc_node+0x380/0x4e0
>     [<0000000099f63f55>] __kmalloc_node_track_caller+0x55/0x140
>     [<00000000c4efe87f>] kvasprintf+0x6b/0xd0
>     [<000000000c0f91cd>] kasprintf+0x4e/0x70
>     [<000000003434d9b5>] gpio_sim_device_config_live_store+0x401/0x59d [gpio_sim]
>     [<0000000052ce6759>] configfs_write_iter+0xcc/0x130
>     [<0000000006087fd2>] vfs_write+0x2b4/0x3d0
>     [<000000008a17e041>] ksys_write+0x61/0xe0
>     [<000000007bded8ea>] __x64_sys_write+0x1a/0x20
>     [<00000000e1220148>] do_syscall_64+0x58/0x80
>     [<0000000006093069>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> real	2m16.398s
> user	0m0.023s
> sys	0m16.360s
> root@/home/user/kernel_bugs/gpio-sim# 
> 
> The effect is cummulative:
> 
> root@marvin-IdeaPad-3-15ITL6:/home/user/kernel_bugs/gpio-sim# cat /sys/kernel/debug/kmemleak 
> unreferenced object 0xffff9593b9d16bc0 (size 32):
>   comm "gpio-reproduce-", pid 7594, jiffies 4295865460 (age 520.296s)
>   hex dump (first 32 bytes):
>     67 70 69 6f 2d 73 69 6d 2e 30 2d 6e 6f 64 65 30  gpio-sim.0-node0
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<00000000fe76444b>] __kmem_cache_alloc_node+0x380/0x4e0
>     [<0000000099f63f55>] __kmalloc_node_track_caller+0x55/0x140
>     [<00000000c4efe87f>] kvasprintf+0x6b/0xd0
>     [<000000000c0f91cd>] kasprintf+0x4e/0x70
>     [<000000003434d9b5>] gpio_sim_device_config_live_store+0x401/0x59d [gpio_sim]
>     [<0000000052ce6759>] configfs_write_iter+0xcc/0x130
>     [<0000000006087fd2>] vfs_write+0x2b4/0x3d0
>     [<000000008a17e041>] ksys_write+0x61/0xe0
>     [<000000007bded8ea>] __x64_sys_write+0x1a/0x20
>     [<00000000e1220148>] do_syscall_64+0x58/0x80
>     [<0000000006093069>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> unreferenced object 0xffff95938918fb40 (size 32):
>   comm "gpio-reproduce-", pid 7675, jiffies 4295954327 (age 164.832s)
>   hex dump (first 32 bytes):
>     67 70 69 6f 2d 73 69 6d 2e 30 2d 6e 6f 64 65 30  gpio-sim.0-node0
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<00000000fe76444b>] __kmem_cache_alloc_node+0x380/0x4e0
>     [<0000000099f63f55>] __kmalloc_node_track_caller+0x55/0x140
>     [<00000000c4efe87f>] kvasprintf+0x6b/0xd0
>     [<000000000c0f91cd>] kasprintf+0x4e/0x70
>     [<000000003434d9b5>] gpio_sim_device_config_live_store+0x401/0x59d [gpio_sim]
>     [<0000000052ce6759>] configfs_write_iter+0xcc/0x130
>     [<0000000006087fd2>] vfs_write+0x2b4/0x3d0
>     [<000000008a17e041>] ksys_write+0x61/0xe0
>     [<000000007bded8ea>] __x64_sys_write+0x1a/0x20
>     [<00000000e1220148>] do_syscall_64+0x58/0x80
>     [<0000000006093069>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> unreferenced object 0xffff9594a3cf1820 (size 32):
>   comm "gpio-reproduce-", pid 7721, jiffies 4295976853 (age 74.728s)
>   hex dump (first 32 bytes):
>     67 70 69 6f 2d 73 69 6d 2e 30 2d 6e 6f 64 65 30  gpio-sim.0-node0
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<00000000fe76444b>] __kmem_cache_alloc_node+0x380/0x4e0
>     [<0000000099f63f55>] __kmalloc_node_track_caller+0x55/0x140
>     [<00000000c4efe87f>] kvasprintf+0x6b/0xd0
>     [<000000000c0f91cd>] kasprintf+0x4e/0x70
>     [<000000003434d9b5>] gpio_sim_device_config_live_store+0x401/0x59d [gpio_sim]
>     [<0000000052ce6759>] configfs_write_iter+0xcc/0x130
>     [<0000000006087fd2>] vfs_write+0x2b4/0x3d0
>     [<000000008a17e041>] ksys_write+0x61/0xe0
>     [<000000007bded8ea>] __x64_sys_write+0x1a/0x20
>     [<00000000e1220148>] do_syscall_64+0x58/0x80
>     [<0000000006093069>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> root@marvin-IdeaPad-3-15ITL6:/home/user/kernel_bugs/gpio-sim# 
> 
> With sufficient privileges (or possibly even without them), an exploit can be devised
> to automate allocation of orphaned objects, at a rate of a couple per second (PoC attached).

Looking into the code I found one inconsistency. It might be that that brings
an issue, dunno. Can you try the patch below if it helps (but TBH I'm a bit
sceptical)?