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b=itXByRbw+mP3n0WYUFSgOvuNWwiQkJMyZndGej1Q+qst31PJZbH6hK5bKQPa8pye+ 8z8HSlCAtj0uObcAzFM41I0i1eME3B6Bi8ajwvxrJYfYLrghnHBDvJdiJzElpB6dgx 6udxDWvfBe/N7Wnl4Rg3vu7KbiWdMEYlpoOK3B2DJ+t01suWb5DaAsMMK3B1krviAH GxhO/AdojFJgoYBSOPNzAhbQgIYy8pkvAB/sTodPhcLgM7fa7Xy/FT1idtC3pqgPAF zAo5rkvorkJD1JryB7ndb0kXfNlZDrLT21DM1MHfbYKs+V+EtGAisgsYyQwcWj+KKU ozSnoW+MLfQsA== From: Pratyush Yadav To: George Guo Cc: chenhuacai@kernel.org, rppt@kernel.org, pasha.tatashin@soleen.com, pratyush@kernel.org, kernel@xen0n.name, graf@amazon.com, shuah@kernel.org, loongarch@lists.linux.dev, kexec@lists.infradead.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, George Guo Subject: Re: [PATCH 2/7] LoongArch: kho: strip stale kho_handover= from reused cmdline In-Reply-To: <20260525062810.103367-3-dongtai.guo@linux.dev> (George Guo's message of "Mon, 25 May 2026 14:28:05 +0800") References: <20260525062810.103367-1-dongtai.guo@linux.dev> <20260525062810.103367-3-dongtai.guo@linux.dev> Date: Mon, 25 May 2026 19:49:28 +0200 Message-ID: <2vxzpl2j5qhj.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Stat-Signature: 5ws7kfsbszg7wupoxnj5wsqao19urtkg X-Rspamd-Queue-Id: E5949C000D X-Rspamd-Server: rspam07 X-Rspam-User: X-HE-Tag: 1779731372-767163 X-HE-Meta: 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 YReFuExX SQEkRHj1uwZ6EcJnJGGEwGID0nimo39K36ogfgoSsPSJuZC0S13NKiV8ncXBm8LQBmgE6n9iGqqlP2jp9UHKOWaVcJpfJ5TeTjXwv6pa8KlS8myUpsjcToy4Dca0adTDifTEPlr/J8Pe4JfBqoTuTLBH7awGlVuEia/fmTUm+x0A8Sz/6y6w6SDd+eu7gxObnceWlXg+rWVgrlJkSUGRmEHRyUQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, May 25 2026, George Guo wrote: > From: George Guo > > When kexec is invoked with --reuse-cmdline after a liveupdate boot, the > running kernel's command line already contains a kho_handover= parameter > from the previous kexec load. load_other_segments() prepends a fresh > kho_handover= for the new handover FDT but then appends the original > cmdline verbatim, resulting in two kho_handover= entries: > > kho_handover=0x4000@,... kho_handover=0x4000@,... > > early_param() calls early_parse_kho() for each occurrence in order, so > kho_populate() is invoked twice and the second call overwrites the first > with the stale FDT address. The stale address no longer holds a valid > KHO FDT, causing __kho_radix_walk_tree() to dereference a garbage > pointer and panic early in mm_core_init(). > > Fix this by adding the new kho_handover= to the cmdline prefix first, > then stripping any stale kho_handover= tokens from the appended original > cmdline portion, so only the freshly generated entry survives. > > Signed-off-by: George Guo > --- > arch/loongarch/kernel/machine_kexec_file.c | 35 ++++++++++++++++++++++ > 1 file changed, 35 insertions(+) > > diff --git a/arch/loongarch/kernel/machine_kexec_file.c b/arch/loongarch/kernel/machine_kexec_file.c > index ddf4d0e0e7fd..ffaedd055e62 100644 > --- a/arch/loongarch/kernel/machine_kexec_file.c > +++ b/arch/loongarch/kernel/machine_kexec_file.c > @@ -71,6 +71,37 @@ static void cmdline_add_kho(struct kimage *image, unsigned long *cmdline_tmplen, > image->kho.scratch->bufsz, (u64)image->kho.scratch->mem); > *cmdline_tmplen += n; > } > + > +/* > + * Remove all "kho_handover=..." tokens from cmdline. Needed when > + * --reuse-cmdline is used: the running kernel's cmdline already carries a > + * stale kho_handover= from the previous kexec load; without removal the new > + * kernel sees two entries and kho_populate() ends up using the wrong (stale) > + * FDT address. > + */ > +static void cmdline_remove_kho(char *cmdline) > +{ > + const char *key = "kho_handover="; > + size_t key_len = strlen(key); > + char *p = cmdline; > + > + while ((p = strstr(p, key)) != NULL) { > + char *start = p; > + char *end; > + > + /* Only match at a token boundary */ > + if (start != cmdline && *(start - 1) != ' ') { > + p += key_len; > + continue; > + } > + end = start + key_len; > + while (*end && *end != ' ') > + end++; > + while (*end == ' ') > + end++; > + memmove(start, end, strlen(end) + 1); > + } > +} Ugh, modifying the commandline supplied by userspace feels odd... Can you at all do this via device tree? If not, would it make more sense to reject kexec_load if command line has kho_handover= and teach kexec-tools to strip it on its side? > #endif > > #ifdef CONFIG_CRASH_DUMP > @@ -249,6 +280,10 @@ int load_other_segments(struct kimage *image, > } > > memcpy(modified_cmdline + cmdline_tmplen, cmdline, cmdline_len); > +#ifdef CONFIG_KEXEC_HANDOVER > + /* Strip stale kho_handover= that --reuse-cmdline may have carried over */ > + cmdline_remove_kho(modified_cmdline + cmdline_tmplen); > +#endif > cmdline = modified_cmdline; > image->arch.cmdline_ptr = (unsigned long)cmdline; -- Regards, Pratyush Yadav