Messages in this thread | | | From | Yuntao Wang <> | Subject | Re: [PATCH] init/main.c: Fix potential static_command_line memory overflow | Date | Thu, 11 Apr 2024 23:47:41 +0800 |
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On Fri, 12 Apr 2024 00:08:58 +0900, Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> On Thu, 11 Apr 2024 22:27:23 +0800 > Yuntao Wang <ytcoode@gmail.com> wrote: > > > On Thu, 11 Apr 2024 16:21:37 +0300, Mike Rapoport <rppt@kernel.org> wrote: > > > On Thu, Apr 11, 2024 at 09:23:47AM +0200, Geert Uytterhoeven wrote: > > > > CC Hiramatsu-san > > > > > > > > On Thu, Apr 11, 2024 at 5:25 AM Yuntao Wang <ytcoode@gmail.com> wrote: > > > > > We allocate memory of size 'xlen + strlen(boot_command_line) + 1' for > > > > > static_command_line, but the strings copied into static_command_line are > > > > > extra_command_line and command_line, rather than extra_command_line and > > > > > boot_command_line. > > > > > > > > > > When strlen(command_line) > strlen(boot_command_line), static_command_line > > > > > will overflow. > > > > > > Can this ever happen? > > > Did you observe the overflow or is this a theoretical bug? > > > > I didn't observe the overflow, it's just a theoretical bug. > > > > > > > Fixes: f5c7310ac73e ("init/main: add checks for the return value of memblock_alloc*()") > > > > > > f5c7310ac73e didn't have the logic for calculating allocation size, we > > > surely don't want to go back that far wiht Fixes. > > > > Before commit f5c7310ac73e, the memory size allocated for static_command_line > > was 'strlen(command_line) + 1', but commit f5c7310ac73e changed this size > > to 'strlen(boot_command_line) + 1'. I think this should be wrong. > > Ah, OK. that sounds reasonable.
:-)
> > > > > > > Signed-off-by: Yuntao Wang <ytcoode@gmail.com> > > > > > --- > > > > > init/main.c | 8 +++++--- > > > > > 1 file changed, 5 insertions(+), 3 deletions(-) > > > > > > > > > > diff --git a/init/main.c b/init/main.c > > > > > index 2ca52474d0c3..a7b1f5f3e3b6 100644 > > > > > --- a/init/main.c > > > > > +++ b/init/main.c > > > > > @@ -625,11 +625,13 @@ static void __init setup_command_line(char *command_line) > > > > > if (extra_init_args) > > > > > ilen = strlen(extra_init_args) + 4; /* for " -- " */ > > > > > > > > > > - len = xlen + strlen(boot_command_line) + 1; > > > > > + len = xlen + strlen(boot_command_line) + ilen + 1; > > > > > > > > > > - saved_command_line = memblock_alloc(len + ilen, SMP_CACHE_BYTES); > > > > > + saved_command_line = memblock_alloc(len, SMP_CACHE_BYTES); > > > > > if (!saved_command_line) > > > > > - panic("%s: Failed to allocate %zu bytes\n", __func__, len + ilen); > > > > > + panic("%s: Failed to allocate %zu bytes\n", __func__, len); > > > > > + > > > > > + len = xlen + strlen(command_line) + 1; > > Ah, I missed this line. Sorry. So this looks good to me but you don't need any > other lines, because those are not related to the bug you want to fix. > Please just focus on 1 fix. > > Thank you,
The other few lines of modification are some very small optimization. I thought they were not worth posting a separate patch for at the time, so I post them together. If necessary, I can separate them.
Thanks.
> > > > > > > > > > static_command_line = memblock_alloc(len, SMP_CACHE_BYTES); > > > > > if (!static_command_line) > > > > > > > > Gr{oetje,eeting}s, > > > > > > > > Geert > > > > > > > > -- > > > > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org > > > > > > > > In personal conversations with technical people, I call myself a hacker. But > > > > when I'm talking to journalists I just say "programmer" or something like that. > > > > -- Linus Torvalds > > > > > > -- > > > Sincerely yours, > > > Mike. > > > -- > Masami Hiramatsu (Google) <mhiramat@kernel.org>
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