From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Andrey Skvortsov <andrej.skvortzov@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Jens Axboe <axboe@kernel.dk>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] zram: don't free statically defined names
Date: Tue, 24 Sep 2024 00:34:49 +0900 [thread overview]
Message-ID: <20240923153449.GC38742@google.com> (raw)
In-Reply-To: <20240923080211.820185-1-andrej.skvortzov@gmail.com>
On (24/09/23 11:02), Andrey Skvortsov wrote:
> The change is similar to that is used in comp_algorithm_set.
> This is detected by KASAN.
>
> ==================================================================
---8<---
> Unable to handle kernel paging request at virtual address ffffffffc1edc3c8
> KASAN: maybe wild-memory-access in range
> [0x0003fffe0f6e1e40-0x0003fffe0f6e1e47]
> Mem abort info:
> ESR = 0x0000000096000006
> EC = 0x25: DABT (current EL), IL = 32 bits
> SET = 0, FnV = 0
> EA = 0, S1PTW = 0
> FSC = 0x06: level 2 translation fault
> Data abort info:
> ISV = 0, ISS = 0x00000006, ISS2 = 0x00000000
> CM = 0, WnR = 0, TnD = 0, TagAccess = 0
> GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> swapper pgtable: 4k pages, 48-bit VAs, pgdp=00000000427dc000
> [ffffffffc1edc3c8] pgd=00000000430e7003, p4d=00000000430e7003,
> pud=00000000430e8003, pmd=0000000000000000
> Internal error: Oops: 0000000096000006 [#1] SMP
>
> Tainted: [W]=WARN, [C]=CRAP, [N]=TEST
> Hardware name: Pine64 PinePhone (1.2) (DT)
> pstate: a0000005 (NzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : kfree+0x60/0x3a0
> lr : zram_destroy_comps+0x98/0x198 [zram]
> sp : ffff800089b57450
> x29: ffff800089b57460 x28: 0000000000000004 x27: ffff800082833010
> x26: 1fffe00000c8039c x25: 1fffe00000ba5004 x24: ffff000005d28000
> x23: ffff800082533178 x22: ffff80007b71eaa8 x21: ffff000006401ce8
> x20: ffff80007b70f7a0 x19: ffffffffc1edc3c0 x18: 1ffff00010506d6b
> x17: 0000000000000000 x16: 0000000000000000 x15: ffff8000808e85e4
> x14: ffff8000808e8478 x13: ffff80008003fa50 x12: ffff80008003f87c
> x11: ffff800080011550 x10: ffff800081ee63f0 x9 : ffff80007b71eaa8
> x8 : ffff80008003fa50 x7 : ffff80008003f87c x6 : 00000018a10e2f30
> x5 : 00ffffffffffffff x4 : ffff00000ec93200 x3 : ffff00000bbee6e0
> x2 : 0000000000000000 x1 : 0000000000000000 x0 : fffffdffc0000000
---8<---
The above is not needed in the commit message (not even sure if the
backtrace below is relevant).
> Call trace:
> kfree+0x60/0x3a0
> zram_destroy_comps+0x98/0x198 [zram]
> zram_reset_device+0x22c/0x4a8 [zram]
> reset_store+0x1bc/0x2d8 [zram]
> dev_attr_store+0x44/0x80
> sysfs_kf_write+0xfc/0x188
> kernfs_fop_write_iter+0x28c/0x428
> vfs_write+0x4dc/0x9b8
> ksys_write+0x100/0x1f8
> __arm64_sys_write+0x74/0xb8
> invoke_syscall+0xd8/0x260
> el0_svc_common.constprop.0+0xb4/0x240
> do_el0_svc+0x48/0x68
> el0_svc+0x40/0xc8
> el0t_64_sync_handler+0x120/0x130
> el0t_64_sync+0x190/0x198
[..]
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index c3d245617083d..d9d2c36658f59 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -2116,7 +2116,9 @@ static void zram_destroy_comps(struct zram *zram)
> }
>
> for (prio = ZRAM_SECONDARY_COMP; prio < ZRAM_MAX_COMPS; prio++) {
> - kfree(zram->comp_algs[prio]);
> + /* Do not free statically defined compression algorithms */
We probably don't really need this comment.
> + if (zram->comp_algs[prio] != default_compressor)
> + kfree(zram->comp_algs[prio]);
> zram->comp_algs[prio] = NULL;
> }
OK, so... I wonder how do you get a `default_compressor` on a
non-ZRAM_PRIMARY_COMP prio. May I ask what's your reproducer?
I didn't expect `default_compressor` on ZRAM_SECONDARY_COMP
and below. As far as I can tell, we only do this:
comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor);
in zram_reset_device() and zram_add(). So, how does it end up in
ZRAM_SECONDARY_COMP...
next prev parent reply other threads:[~2024-09-23 15:34 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-23 8:02 [PATCH] zram: don't free statically defined names Andrey Skvortsov
2024-09-23 15:34 ` Sergey Senozhatsky [this message]
2024-09-23 15:47 ` Sergey Senozhatsky
2024-09-23 15:55 ` Andrey Skvortsov
2024-09-23 16:07 ` Sergey Senozhatsky
2024-09-23 16:43 ` Andrey Skvortsov
2024-09-23 16:47 ` Christophe JAILLET
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