Hi, Kazu
Thank you for the fix.
On Thu, Dec 5, 2024 at 5:10 PM <devel-requ...@lists.crash-utility.osci.io>
wrote:
> Date: Thu, 5 Dec 2024 01:30:34 +0000
> From: HAGIO KAZUHITO(萩尾 一仁) <k-hagio...@nec.com>
> Subject: [Crash-utility] [PATCH] Fix infinite loop during module
> symbols initialization
> To: "devel@lists.crash-utility.osci.io"
> <devel@lists.crash-utility.osci.io>
> Message-ID: <1733362232-30303-1-git-send-email-k-hagio...@nec.com>
> Content-Type: text/plain; charset="iso-2022-jp"
>
> From: Kazuhito Hagio <k-hagio...@nec.com>
>
> An infinite loop occured in mod_symname_hash_install() during module
> symbols initialization on 6.13-rc1 kernel.
>
> Not sure which kernel patch caused this (probably execmem patches), a
> gap region between a module text and another module's one has gone, i.e.
> they became consecutive. In this case, as we set a module's pseudo end
> symbol to "base + size" value, it's equal to another module's pseudo
> start symbol. This and qsort() for st->ext_module_symbtable cause
> region overlaps like this:
>
> sp sp->value sp->name
> 823ac68 ffffffffc0800000 _MODULE_TEXT_START_dm_mod
> ...
> 8242080 ffffffffc0814ad0 __pfx_dm_devt_from_path
> 82420a8 ffffffffc0814ae0 dm_devt_from_path
> 82420d0 ffffffffc0815000 _MODULE_TEXT_START_libcrc32c << same value
> 82420f8 ffffffffc0815000 __pfx_crc32c << and
> 8242120 ffffffffc0815000 _MODULE_TEXT_END_dm_mod << overlap
>
Strange, this looks like a kernel module issue?
> 8242148 ffffffffc0815010 crc32c
> 8242170 ffffffffc0815080 __pfx_libcrc32c_mod_fini
> ...
> 8242238 ffffffffc0816000 _MODULE_TEXT_END_libcrc32c
>
> As a result, mod_symtable_hash_install_range() can add a module symbol
> two times, which makes a self-loop. This causes an infinite loop in
> mod_symname_hash_install().
>
> Core was generated by `crash'.
> #0 mod_symname_hash_install (spn=0x75e6bc0) at symbols.c:1236
> 1236 if (!sp->name_hash_next ||
> (gdb) p sp
> $1 = (struct syment *) 0x75e6670
> (gdb) p sp->name
> $2 = 0x7c03573 "_MODULE_TEXT_START_libcrc32c"
> (gdb) p sp->name_hash_next
> $3 = (struct syment *) 0x75e6670 << self-loop
>
> To avoid this, fix module pseudo end symbols to "base + size - 1".
>
>
So far I haven't thought of a better solution yet. For the patch: Ack.
Thanks
Lianbo
> Signed-off-by: Kazuhito Hagio <k-hagio...@nec.com>
> ---
> symbols.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/symbols.c b/symbols.c
> index a26bdc1a3461..0fe5d2951c7e 100644
> --- a/symbols.c
> +++ b/symbols.c
> @@ -2196,7 +2196,7 @@ store_module_symbols_6_4(ulong total, int
> mods_installed)
> if (!lm->mem[t].size)
> continue;
>
> - st->ext_module_symtable[mcnt].value =
> lm->mem[t].base + lm->mem[t].size;
> + st->ext_module_symtable[mcnt].value =
> lm->mem[t].base + lm->mem[t].size - 1;
st->ext_module_symtable[mcnt].type = 'm';
> st->ext_module_symtable[mcnt].flags |=
> MODULE_SYMBOL;
> sprintf(buf2, "%s%s", module_tag[t].end, mod_name);
> --
> 2.31.1
>
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