Acked-by: Jolly Shah <[email protected]>
> -----Original Message----- > From: Jann Horn <[email protected]> > Sent: Monday, February 18, 2019 1:43 PM > To: Michal Simek <[email protected]>; [email protected] > Cc: Rajan Vaja <[email protected]>; Jolly Shah <[email protected]>; linux- > [email protected]; [email protected] > Subject: [PATCH] firmware: xilinx: fix debugfs write handler > > - Userspace wants to write a string with `len` bytes, not counting the > terminating NULL, so we should allocate `len+1` bytes. It looks like the > current code relied on having a nullbyte directly behind `kern_buff`, > which happens to work reliably as long as `len` isn't one of the kmalloc > size classes. > - strncpy_from_user() is completely wrong here; userspace is giving us a > (not necessarily null-terminated) buffer and its length. > strncpy_from_user() is for cases in which we don't know the length. > - Don't let broken userspace allocate arbitrarily big kmalloc allocations. > > Just use memdup_user_nul(), which is designed precisely for things like > this. > > Signed-off-by: Jann Horn <[email protected]> > --- > WARNING: completely untested patch > > drivers/firmware/xilinx/zynqmp-debug.c | 15 ++++----------- > 1 file changed, 4 insertions(+), 11 deletions(-) > > diff --git a/drivers/firmware/xilinx/zynqmp-debug.c > b/drivers/firmware/xilinx/zynqmp-debug.c > index 2771df6df379..90b66cdbfd58 100644 > --- a/drivers/firmware/xilinx/zynqmp-debug.c > +++ b/drivers/firmware/xilinx/zynqmp-debug.c > @@ -163,21 +163,14 @@ static ssize_t zynqmp_pm_debugfs_api_write(struct > file *file, > > strcpy(debugfs_buf, ""); > > - if (*off != 0 || len == 0) > + if (*off != 0 || len <= 1 || len > PAGE_SIZE - 1) > return -EINVAL; > > - kern_buff = kzalloc(len, GFP_KERNEL); > - if (!kern_buff) > - return -ENOMEM; > - > + kern_buff = memdup_user_nul(ptr, len); > + if (IS_ERR(kern_buff)) > + return PTR_ERR(kern_buff); > tmp_buff = kern_buff; > > - ret = strncpy_from_user(kern_buff, ptr, len); > - if (ret < 0) { > - ret = -EFAULT; > - goto err; > - } > - > /* Read the API name from a user request */ > pm_api_req = strsep(&kern_buff, " "); > > -- > 2.21.0.rc0.258.g878e2cd30e-goog
