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([144.202.108.46]) by smtp.gmail.com with ESMTPSA id s3-20020a170902ea0300b001e294f2f30dsm1228876plg.93.2024.04.11.07.27.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Apr 2024 07:27:50 -0700 (PDT) From: Yuntao Wang To: rppt@kernel.org Cc: akpm@linux-foundation.org, arnd@arndb.de, christophe.leroy@csgroup.eu, geert@linux-m68k.org, jpoimboe@kernel.org, kjlx@templeofstupid.com, linux-kernel@vger.kernel.org, mhiramat@kernel.org, ndesaulniers@google.com, peterz@infradead.org, tglx@linutronix.de, tj@kernel.org, ytcoode@gmail.com Subject: Re: [PATCH] init/main.c: Fix potential static_command_line memory overflow Date: Thu, 11 Apr 2024 22:27:23 +0800 Message-ID: <20240411142735.245515-1-ytcoode@gmail.com> X-Mailer: git-send-email 2.44.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On Thu, 11 Apr 2024 16:21:37 +0300, Mike Rapoport 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 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. > > > Signed-off-by: Yuntao Wang > > > --- > > > 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; > > > > > > 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.