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Sat, 22 Aug 2026 02:51:28 -0700 (PDT) Received: from localhost.localdomain ([101.251.7.10]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-327f91d2d1esm5244881eec.17.2026.08.22.02.51.24 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Sat, 22 Aug 2026 02:51:27 -0700 (PDT) From: Laxman Acharya Padhya To: Sven Peter , Janne Grunau Cc: Neal Gompa , asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH] soc: apple: rtkit: bound syslog copies to the shared buffer Date: Sat, 22 Aug 2026 15:36:21 +0545 Message-ID: <20260822095121.53451-1-acharyalaxman8848@gmail.com> X-Mailer: git-send-email 2.51.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" apple_rtkit_syslog_rx_log() copies a log entry out of the coprocessor shared-memory ring using an index and layout that the coprocessor itself chose (SYSLOG_INIT n_entries / msg_size, plus the 8-bit idx in the LOG message). Those values are never checked against syslog_buffer.size, so a compromised or buggy RTKit firmware can make the kernel memcpy_fromio()/memcpy() past the DMA mapping. SYSLOG_INIT also accepted msg_size =3D=3D 0. kzalloc(0) returns ZERO_SIZE_PTR, which is non-NULL, and strnlen(..., msg_size - 1) then wraps to SIZE_MAX. Treat n_entries as a count (reject idx >=3D n_entries), reject a zero message size, and refuse shared-memory copies that do not fit in the buffer. Rate-limit the new OOB warning so a coprocessor cannot flood the kernel log. Fixes: 9bd1d9a0d8bb ("soc: apple: Add RTKit IPC library") Cc: stable@vger.kernel.org Signed-off-by: Laxman Acharya Padhya --- drivers/soc/apple/rtkit.c | 73 ++++++++++++++++++++++++++++++--------- 1 file changed, 56 insertions(+), 17 deletions(-) diff --git a/drivers/soc/apple/rtkit.c b/drivers/soc/apple/rtkit.c index a3fdac8f6f06..63b85d082a7a 100644 --- a/drivers/soc/apple/rtkit.c +++ b/drivers/soc/apple/rtkit.c @@ -348,14 +348,28 @@ static void apple_rtkit_free_buffer(struct apple_rtki= t *rtk, bfr->is_mapped =3D false; } =20 -static void apple_rtkit_memcpy(struct apple_rtkit *rtk, void *dst, - struct apple_rtkit_shmem *bfr, size_t offset, - size_t len) +static bool apple_rtkit_shmem_ok(struct apple_rtkit_shmem *bfr, size_t off= set, + size_t len) { + return offset <=3D bfr->size && len <=3D bfr->size - offset; +} + +static int apple_rtkit_memcpy(struct apple_rtkit *rtk, void *dst, + struct apple_rtkit_shmem *bfr, size_t offset, + size_t len) +{ + if (!apple_rtkit_shmem_ok(bfr, offset, len)) { + dev_warn_ratelimited(rtk->dev, + "RTKit: shared-memory copy out of bounds (off 0x%zx len 0x%zx siz= e 0x%zx)\n", + offset, len, bfr->size); + return -EINVAL; + } + if (bfr->iomem) memcpy_fromio(dst, bfr->iomem + offset, len); else memcpy(dst, bfr->buffer + offset, len); + return 0; } =20 static void apple_rtkit_crashlog_rx(struct apple_rtkit *rtk, u64 msg) @@ -384,9 +398,10 @@ static void apple_rtkit_crashlog_rx(struct apple_rtkit= *rtk, u64 msg) */ bfr =3D kzalloc(rtk->crashlog_buffer.size, GFP_KERNEL); if (bfr) { - apple_rtkit_memcpy(rtk, bfr, &rtk->crashlog_buffer, 0, - rtk->crashlog_buffer.size); - apple_rtkit_crashlog_dump(rtk, bfr, rtk->crashlog_buffer.size); + if (!apple_rtkit_memcpy(rtk, bfr, &rtk->crashlog_buffer, 0, + rtk->crashlog_buffer.size)) + apple_rtkit_crashlog_dump(rtk, bfr, + rtk->crashlog_buffer.size); } else { dev_err(rtk->dev, "RTKit: Couldn't allocate crashlog shadow buffer\n"); @@ -422,10 +437,29 @@ static void apple_rtkit_ioreport_rx(struct apple_rtki= t *rtk, u64 msg) =20 static void apple_rtkit_syslog_rx_init(struct apple_rtkit *rtk, u64 msg) { - rtk->syslog_n_entries =3D FIELD_GET(APPLE_RTKIT_SYSLOG_N_ENTRIES, msg); - rtk->syslog_msg_size =3D FIELD_GET(APPLE_RTKIT_SYSLOG_MSG_SIZE, msg); + size_t n_entries =3D FIELD_GET(APPLE_RTKIT_SYSLOG_N_ENTRIES, msg); + size_t msg_size =3D FIELD_GET(APPLE_RTKIT_SYSLOG_MSG_SIZE, msg); =20 - rtk->syslog_msg_buffer =3D kzalloc(rtk->syslog_msg_size, GFP_KERNEL); + kfree(rtk->syslog_msg_buffer); + rtk->syslog_msg_buffer =3D NULL; + rtk->syslog_n_entries =3D 0; + rtk->syslog_msg_size =3D 0; + + /* + * msg_size =3D=3D 0 would make kzalloc() return ZERO_SIZE_PTR (non-NULL) + * and later strnlen(..., msg_size - 1) wrap to SIZE_MAX. + */ + if (!msg_size) { + dev_warn(rtk->dev, "RTKit: syslog msg_size is zero\n"); + return; + } + + rtk->syslog_msg_buffer =3D kzalloc(msg_size, GFP_KERNEL); + if (!rtk->syslog_msg_buffer) + return; + + rtk->syslog_n_entries =3D n_entries; + rtk->syslog_msg_size =3D msg_size; =20 dev_dbg(rtk->dev, "RTKit: syslog initialized: entries: %zd, msg_size: %zd\n", @@ -441,10 +475,11 @@ static void apple_rtkit_syslog_rx_log(struct apple_rt= kit *rtk, u64 msg) { u8 idx =3D msg & 0xff; char log_context[24]; - size_t entry_size =3D 0x20 + rtk->syslog_msg_size; + size_t entry_size; + size_t offset; int msglen; =20 - if (!rtk->syslog_msg_buffer) { + if (!rtk->syslog_msg_buffer || !rtk->syslog_msg_size) { dev_warn( rtk->dev, "RTKit: received syslog message but no syslog_msg_buffer\n"); @@ -462,17 +497,21 @@ static void apple_rtkit_syslog_rx_log(struct apple_rt= kit *rtk, u64 msg) "RTKit: received syslog message but no syslog_buffer.buffer or syslog_b= uffer.iomem\n"); goto done; } - if (idx > rtk->syslog_n_entries) { + if (idx >=3D rtk->syslog_n_entries) { dev_warn(rtk->dev, "RTKit: syslog index %d out of range\n", idx); goto done; } =20 - apple_rtkit_memcpy(rtk, log_context, &rtk->syslog_buffer, - idx * entry_size + 8, sizeof(log_context)); - apple_rtkit_memcpy(rtk, rtk->syslog_msg_buffer, &rtk->syslog_buffer, - idx * entry_size + 8 + sizeof(log_context), - rtk->syslog_msg_size); + entry_size =3D 0x20 + rtk->syslog_msg_size; + offset =3D (size_t)idx * entry_size + 8; + if (apple_rtkit_memcpy(rtk, log_context, &rtk->syslog_buffer, offset, + sizeof(log_context))) + goto done; + if (apple_rtkit_memcpy(rtk, rtk->syslog_msg_buffer, &rtk->syslog_buffer, + offset + sizeof(log_context), + rtk->syslog_msg_size)) + goto done; =20 log_context[sizeof(log_context) - 1] =3D 0; =20 --=20 2.51.2