* [PATCH] zram: fix NULL pointer in comp_algorithm_show()
@ 2024-11-08 10:01 Liu Shixin
2024-11-09 1:12 ` Sergey Senozhatsky
2024-11-10 3:07 ` Jens Axboe
0 siblings, 2 replies; 5+ messages in thread
From: Liu Shixin @ 2024-11-08 10:01 UTC (permalink / raw)
To: Minchan Kim, Sergey Senozhatsky, Jens Axboe, Andrew Morton
Cc: linux-kernel, linux-block, Liu Shixin
LTP reported a NULL pointer dereference as followed:
CPU: 7 UID: 0 PID: 5995 Comm: cat Kdump: loaded Not tainted 6.12.0-rc6+ #3
Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __pi_strcmp+0x24/0x140
lr : zcomp_available_show+0x60/0x100 [zram]
sp : ffff800088b93b90
x29: ffff800088b93b90 x28: 0000000000000001 x27: 0000000000400cc0
x26: 0000000000000ffe x25: ffff80007b3e2388 x24: 0000000000000000
x23: ffff80007b3e2390 x22: ffff0004041a9000 x21: ffff80007b3e2900
x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000000
x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
x11: 0000000000000000 x10: ffff80007b3e2900 x9 : ffff80007b3cb280
x8 : 0101010101010101 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000040 x4 : 0000000000000000 x3 : 00656c722d6f7a6c
x2 : 0000000000000000 x1 : ffff80007b3e2900 x0 : 0000000000000000
Call trace:
__pi_strcmp+0x24/0x140
comp_algorithm_show+0x40/0x70 [zram]
dev_attr_show+0x28/0x80
sysfs_kf_seq_show+0x90/0x140
kernfs_seq_show+0x34/0x48
seq_read_iter+0x1d4/0x4e8
kernfs_fop_read_iter+0x40/0x58
new_sync_read+0x9c/0x168
vfs_read+0x1a8/0x1f8
ksys_read+0x74/0x108
__arm64_sys_read+0x24/0x38
invoke_syscall+0x50/0x120
el0_svc_common.constprop.0+0xc8/0xf0
do_el0_svc+0x24/0x38
el0_svc+0x38/0x138
el0t_64_sync_handler+0xc0/0xc8
el0t_64_sync+0x188/0x190
The zram->comp_algs[ZRAM_PRIMARY_COMP] can be NULL in zram_add() if
comp_algorithm_set() has not been called. User can access the zram device
by sysfs after device_add_disk(), so there is a time window to trigger
the NULL pointer dereference. Move it ahead device_add_disk() to make sure
when user can access the zram device, it is ready. comp_algorithm_set() is
protected by zram->init_lock in other places and no such problem.
Fixes: 7ac07a26dea7 ("zram: preparation for multi-zcomp support")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
---
drivers/block/zram/zram_drv.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index ad9c9bc3ccfc..5223a03cb10e 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -2381,6 +2381,8 @@ static int zram_add(void)
zram->disk->fops = &zram_devops;
zram->disk->private_data = zram;
snprintf(zram->disk->disk_name, 16, "zram%d", device_id);
+ zram_comp_params_reset(zram);
+ comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);
/* Actual capacity set using sysfs (/sys/block/zram<id>/disksize */
set_capacity(zram->disk, 0);
@@ -2388,9 +2390,6 @@ static int zram_add(void)
if (ret)
goto out_cleanup_disk;
- zram_comp_params_reset(zram);
- comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);
-
zram_debugfs_register(zram);
pr_info("Added device: %s\n", zram->disk->disk_name);
return device_id;
--
2.34.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] zram: fix NULL pointer in comp_algorithm_show()
2024-11-08 10:01 [PATCH] zram: fix NULL pointer in comp_algorithm_show() Liu Shixin
@ 2024-11-09 1:12 ` Sergey Senozhatsky
2024-11-09 3:23 ` Liu Shixin
2024-11-10 3:07 ` Jens Axboe
1 sibling, 1 reply; 5+ messages in thread
From: Sergey Senozhatsky @ 2024-11-09 1:12 UTC (permalink / raw)
To: Andrew Morton, Liu Shixin
Cc: Minchan Kim, Sergey Senozhatsky, Jens Axboe, linux-kernel,
linux-block
On (24/11/08 18:01), Liu Shixin wrote:
> LTP reported a NULL pointer dereference as followed:
>
> CPU: 7 UID: 0 PID: 5995 Comm: cat Kdump: loaded Not tainted 6.12.0-rc6+ #3
> Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
> pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : __pi_strcmp+0x24/0x140
> lr : zcomp_available_show+0x60/0x100 [zram]
> sp : ffff800088b93b90
> x29: ffff800088b93b90 x28: 0000000000000001 x27: 0000000000400cc0
> x26: 0000000000000ffe x25: ffff80007b3e2388 x24: 0000000000000000
> x23: ffff80007b3e2390 x22: ffff0004041a9000 x21: ffff80007b3e2900
> x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000000
> x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
> x11: 0000000000000000 x10: ffff80007b3e2900 x9 : ffff80007b3cb280
> x8 : 0101010101010101 x7 : 0000000000000000 x6 : 0000000000000000
> x5 : 0000000000000040 x4 : 0000000000000000 x3 : 00656c722d6f7a6c
> x2 : 0000000000000000 x1 : ffff80007b3e2900 x0 : 0000000000000000
> Call trace:
> __pi_strcmp+0x24/0x140
> comp_algorithm_show+0x40/0x70 [zram]
> dev_attr_show+0x28/0x80
> sysfs_kf_seq_show+0x90/0x140
> kernfs_seq_show+0x34/0x48
> seq_read_iter+0x1d4/0x4e8
> kernfs_fop_read_iter+0x40/0x58
> new_sync_read+0x9c/0x168
> vfs_read+0x1a8/0x1f8
> ksys_read+0x74/0x108
> __arm64_sys_read+0x24/0x38
> invoke_syscall+0x50/0x120
> el0_svc_common.constprop.0+0xc8/0xf0
> do_el0_svc+0x24/0x38
> el0_svc+0x38/0x138
> el0t_64_sync_handler+0xc0/0xc8
> el0t_64_sync+0x188/0x190
The explanation below is more than enough, I think this stack trace
doesn't really show anything new or interesting.
> The zram->comp_algs[ZRAM_PRIMARY_COMP] can be NULL in zram_add() if
> comp_algorithm_set() has not been called. User can access the zram device
> by sysfs after device_add_disk(), so there is a time window to trigger
> the NULL pointer dereference. Move it ahead device_add_disk() to make sure
> when user can access the zram device, it is ready. comp_algorithm_set() is
> protected by zram->init_lock in other places and no such problem.
>
> Fixes: 7ac07a26dea7 ("zram: preparation for multi-zcomp support")
So I think this fixes something much older, probably around e46b8a030d76d
time (2014).
> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
> ---
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] zram: fix NULL pointer in comp_algorithm_show()
2024-11-09 1:12 ` Sergey Senozhatsky
@ 2024-11-09 3:23 ` Liu Shixin
2024-11-09 3:42 ` Sergey Senozhatsky
0 siblings, 1 reply; 5+ messages in thread
From: Liu Shixin @ 2024-11-09 3:23 UTC (permalink / raw)
To: Sergey Senozhatsky, Andrew Morton
Cc: Minchan Kim, Jens Axboe, linux-kernel, linux-block
On 2024/11/9 9:12, Sergey Senozhatsky wrote:
> On (24/11/08 18:01), Liu Shixin wrote:
>> LTP reported a NULL pointer dereference as followed:
>>
>> CPU: 7 UID: 0 PID: 5995 Comm: cat Kdump: loaded Not tainted 6.12.0-rc6+ #3
>> Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
>> pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>> pc : __pi_strcmp+0x24/0x140
>> lr : zcomp_available_show+0x60/0x100 [zram]
>> sp : ffff800088b93b90
>> x29: ffff800088b93b90 x28: 0000000000000001 x27: 0000000000400cc0
>> x26: 0000000000000ffe x25: ffff80007b3e2388 x24: 0000000000000000
>> x23: ffff80007b3e2390 x22: ffff0004041a9000 x21: ffff80007b3e2900
>> x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000000
>> x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
>> x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
>> x11: 0000000000000000 x10: ffff80007b3e2900 x9 : ffff80007b3cb280
>> x8 : 0101010101010101 x7 : 0000000000000000 x6 : 0000000000000000
>> x5 : 0000000000000040 x4 : 0000000000000000 x3 : 00656c722d6f7a6c
>> x2 : 0000000000000000 x1 : ffff80007b3e2900 x0 : 0000000000000000
>> Call trace:
>> __pi_strcmp+0x24/0x140
>> comp_algorithm_show+0x40/0x70 [zram]
>> dev_attr_show+0x28/0x80
>> sysfs_kf_seq_show+0x90/0x140
>> kernfs_seq_show+0x34/0x48
>> seq_read_iter+0x1d4/0x4e8
>> kernfs_fop_read_iter+0x40/0x58
>> new_sync_read+0x9c/0x168
>> vfs_read+0x1a8/0x1f8
>> ksys_read+0x74/0x108
>> __arm64_sys_read+0x24/0x38
>> invoke_syscall+0x50/0x120
>> el0_svc_common.constprop.0+0xc8/0xf0
>> do_el0_svc+0x24/0x38
>> el0_svc+0x38/0x138
>> el0t_64_sync_handler+0xc0/0xc8
>> el0t_64_sync+0x188/0x190
> The explanation below is more than enough, I think this stack trace
> doesn't really show anything new or interesting.
>
>> The zram->comp_algs[ZRAM_PRIMARY_COMP] can be NULL in zram_add() if
>> comp_algorithm_set() has not been called. User can access the zram device
>> by sysfs after device_add_disk(), so there is a time window to trigger
>> the NULL pointer dereference. Move it ahead device_add_disk() to make sure
>> when user can access the zram device, it is ready. comp_algorithm_set() is
>> protected by zram->init_lock in other places and no such problem.
>>
>> Fixes: 7ac07a26dea7 ("zram: preparation for multi-zcomp support")
> So I think this fixes something much older, probably around e46b8a030d76d
> time (2014).
The NULL pointer is introduced when zram->compressor is changed to zram->comp_algs in
7ac07a26dea, where the former is an array of chars and the latter is an array of pointers.
Before that, if we cat comp_algorithm int the time window, we will get a message with no
algorithm selected like this:
cat /sys/block/zram1/comp_algorithm
lzo lz4
>
>> Signed-off-by: Liu Shixin <liushixin2@huawei.com>
>> ---
> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> .
>
Thanks,
.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] zram: fix NULL pointer in comp_algorithm_show()
2024-11-09 3:23 ` Liu Shixin
@ 2024-11-09 3:42 ` Sergey Senozhatsky
0 siblings, 0 replies; 5+ messages in thread
From: Sergey Senozhatsky @ 2024-11-09 3:42 UTC (permalink / raw)
To: Liu Shixin
Cc: Sergey Senozhatsky, Andrew Morton, Minchan Kim, Jens Axboe,
linux-kernel, linux-block
On (24/11/09 11:23), Liu Shixin wrote:
> >> Fixes: 7ac07a26dea7 ("zram: preparation for multi-zcomp support")
> > So I think this fixes something much older, probably around e46b8a030d76d
> > time (2014).
>
> The NULL pointer is introduced when zram->compressor is changed to zram->comp_algs in
> 7ac07a26dea, where the former is an array of chars and the latter is an array of pointers.
> Before that, if we cat comp_algorithm int the time window, we will get a message with no
> algorithm selected like this:
Good point, you are right.
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] zram: fix NULL pointer in comp_algorithm_show()
2024-11-08 10:01 [PATCH] zram: fix NULL pointer in comp_algorithm_show() Liu Shixin
2024-11-09 1:12 ` Sergey Senozhatsky
@ 2024-11-10 3:07 ` Jens Axboe
1 sibling, 0 replies; 5+ messages in thread
From: Jens Axboe @ 2024-11-10 3:07 UTC (permalink / raw)
To: Minchan Kim, Sergey Senozhatsky, Andrew Morton, Liu Shixin
Cc: linux-kernel, linux-block
On Fri, 08 Nov 2024 18:01:47 +0800, Liu Shixin wrote:
> LTP reported a NULL pointer dereference as followed:
>
> CPU: 7 UID: 0 PID: 5995 Comm: cat Kdump: loaded Not tainted 6.12.0-rc6+ #3
> Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
> pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : __pi_strcmp+0x24/0x140
> lr : zcomp_available_show+0x60/0x100 [zram]
> sp : ffff800088b93b90
> x29: ffff800088b93b90 x28: 0000000000000001 x27: 0000000000400cc0
> x26: 0000000000000ffe x25: ffff80007b3e2388 x24: 0000000000000000
> x23: ffff80007b3e2390 x22: ffff0004041a9000 x21: ffff80007b3e2900
> x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000000
> x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
> x11: 0000000000000000 x10: ffff80007b3e2900 x9 : ffff80007b3cb280
> x8 : 0101010101010101 x7 : 0000000000000000 x6 : 0000000000000000
> x5 : 0000000000000040 x4 : 0000000000000000 x3 : 00656c722d6f7a6c
> x2 : 0000000000000000 x1 : ffff80007b3e2900 x0 : 0000000000000000
> Call trace:
> __pi_strcmp+0x24/0x140
> comp_algorithm_show+0x40/0x70 [zram]
> dev_attr_show+0x28/0x80
> sysfs_kf_seq_show+0x90/0x140
> kernfs_seq_show+0x34/0x48
> seq_read_iter+0x1d4/0x4e8
> kernfs_fop_read_iter+0x40/0x58
> new_sync_read+0x9c/0x168
> vfs_read+0x1a8/0x1f8
> ksys_read+0x74/0x108
> __arm64_sys_read+0x24/0x38
> invoke_syscall+0x50/0x120
> el0_svc_common.constprop.0+0xc8/0xf0
> do_el0_svc+0x24/0x38
> el0_svc+0x38/0x138
> el0t_64_sync_handler+0xc0/0xc8
> el0t_64_sync+0x188/0x190
>
> [...]
Applied, thanks!
[1/1] zram: fix NULL pointer in comp_algorithm_show()
commit: 5fcfcd51ea1c1309a673d45f12698dec53ffbd9b
Best regards,
--
Jens Axboe
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2024-11-10 3:07 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2024-11-08 10:01 [PATCH] zram: fix NULL pointer in comp_algorithm_show() Liu Shixin
2024-11-09 1:12 ` Sergey Senozhatsky
2024-11-09 3:23 ` Liu Shixin
2024-11-09 3:42 ` Sergey Senozhatsky
2024-11-10 3:07 ` Jens Axboe
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