Some consoles, like the input console (usually /dev/cs0), don't feature
a puts or putc callback. Trying to echo out of them would thus crash:
barebox@Embest MarS Board i.MX6Dual:/ echo -a /dev/cs0
prefetch abort
pc : [<00000004>] lr : [<4fd05071>]
WARNING: [<...>] (fops_write+0xd/0x10)
WARNING: [<...>] (devfs_write+0x21/0x2a)
WARNING: [<...>] (__write+0xcb/0xf0)
WARNING: [<...>] (write+0x2d/0x68)
WARNING: [<...>] (dputc+0x31/0x34)
WARNING: [<...>] (do_echo+0xcb/0x144)
Fix this by only allowing open(.., O_WRONLY) or open(..., O_RDWR) when
puts is defined. Consoles defining putc are covered by this as well as
those have putc-calling __console_puts assigned as their puts when they
are registered. Now echo -a /dev/cs0 would yield:
open: Operation not permitted
Signed-off-by: Ahmad Fatoum <ahmad@xxxxxx>
---
common/console.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/common/console.c b/common/console.c
index d04aae58f96e..e6e029848d41 100644
--- a/common/console.c
+++ b/common/console.c
@@ -272,6 +272,9 @@ static int fops_open(struct cdev *cdev, unsigned long flags)
{
struct console_device *priv = cdev->priv;
+ if ((flags & (O_WRONLY | O_RDWR)) && !priv->puts )
+ return -EPERM;
+
return console_open(priv);
}
--
2.20.1
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