From 0eb09f737428e482a32a2e31e5e223f2b35a71d3 Mon Sep 17 00:00:00 2001 From: Tyllis Xu Date: Sat, 14 Mar 2026 11:53:54 -0500 Subject: [PATCH] ibmasm: fix OOB reads in command_file_write due to missing size checks The command_file_write() handler allocates a kernel buffer of exactly count bytes and copies user data into it, but does not validate the buffer against the dot command protocol before passing it to get_dot_command_size() and get_dot_command_timeout(). Since both the allocation size (count) and the header fields (command_size, data_size) are independently user-controlled, an attacker can cause get_dot_command_size() to return a value exceeding the allocation, triggering OOB reads in get_dot_command_timeout() and an out-of-bounds memcpy_toio() that leaks kernel heap memory to the service processor. Fix with two guards: reject writes smaller than sizeof(struct dot_command_header) before allocation, then after copying user data reject commands where the buffer is smaller than the total size declared by the header (sizeof(header) + command_size + data_size). This ensures all subsequent header and payload field accesses stay within the buffer. 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/20260314165355.548119-1-LivelyCarpet87@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/misc/ibmasm/ibmasmfs.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/misc/ibmasm/ibmasmfs.c b/drivers/misc/ibmasm/ibmasmfs.c index f68a8957b98f8..dfdfa9ba47479 100644 --- a/drivers/misc/ibmasm/ibmasmfs.c +++ b/drivers/misc/ibmasm/ibmasmfs.c @@ -303,6 +303,8 @@ static ssize_t command_file_write(struct file *file, const char __user *ubuff, s return -EINVAL; if (count == 0 || count > IBMASM_CMD_MAX_BUFFER_SIZE) return 0; + if (count < sizeof(struct dot_command_header)) + return -EINVAL; if (*offset != 0) return 0; @@ -319,6 +321,11 @@ static ssize_t command_file_write(struct file *file, const char __user *ubuff, s return -EFAULT; } + if (count < get_dot_command_size(cmd->buffer)) { + command_put(cmd); + return -EINVAL; + } + spin_lock_irqsave(&command_data->sp->lock, flags); if (command_data->command) { spin_unlock_irqrestore(&command_data->sp->lock, flags); -- 2.47.3