From: Tyllis Xu Date: Sat, 14 Mar 2026 16:58:05 +0000 (-0500) Subject: ibmasm: fix heap over-read in ibmasm_send_i2o_message() X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9aad71144fa3682cca3837a06c8623016790e7ec;p=thirdparty%2Flinux.git ibmasm: fix heap over-read in ibmasm_send_i2o_message() The ibmasm_send_i2o_message() function uses get_dot_command_size() to compute the byte count for memcpy_toio(), but this value is derived from user-controlled fields in the dot_command_header (command_size: u8, data_size: u16) and is never validated against the actual allocation size. A root user can write a small buffer with inflated header fields, causing memcpy_toio() to read up to ~65 KB past the end of the allocation into adjacent kernel heap, which is then forwarded to the service processor over MMIO. Silently clamping the copy size is not sufficient: if the header fields claim a larger size than the buffer, the SP receives a dot command whose own header is inconsistent with the I2O message length, which can cause the SP to desynchronize. Reject such commands outright by returning failure. Validate command_size before calling get_mfa_inbound() to avoid leaking an I2O message frame: reading INBOUND_QUEUE_PORT dequeues a hardware frame from the controller's free pool, and returning without a corresponding set_mfa_inbound() call would permanently exhaust it. Additionally, clamp command_size to I2O_COMMAND_SIZE before the memcpy_toio() so the MMIO write stays within the I2O message frame, consistent with the clamping already performed by outgoing_message_size() for the header field. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: Yuhao Jiang Cc: stable@vger.kernel.org Signed-off-by: Tyllis Xu Link: https://patch.msgid.link/20260314165805.548293-1-LivelyCarpet87@gmail.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/misc/ibmasm/lowlevel.c b/drivers/misc/ibmasm/lowlevel.c index 6922dc6c10db..5313230f36ad 100644 --- a/drivers/misc/ibmasm/lowlevel.c +++ b/drivers/misc/ibmasm/lowlevel.c @@ -19,17 +19,21 @@ static struct i2o_header header = I2O_HEADER_TEMPLATE; int ibmasm_send_i2o_message(struct service_processor *sp) { u32 mfa; - unsigned int command_size; + size_t command_size; struct i2o_message *message; struct command *command = sp->current_command; + command_size = get_dot_command_size(command->buffer); + if (command_size > command->buffer_size) + return 1; + if (command_size > I2O_COMMAND_SIZE) + command_size = I2O_COMMAND_SIZE; + mfa = get_mfa_inbound(sp->base_address); if (!mfa) return 1; - command_size = get_dot_command_size(command->buffer); - header.message_size = outgoing_message_size(command_size); - + header.message_size = outgoing_message_size((unsigned int)command_size); message = get_i2o_message(sp->base_address, mfa); memcpy_toio(&message->header, &header, sizeof(struct i2o_header));