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printk_ringbuffer: Add sanity check for 0-size data 

get_data() has a sanity check for regular data blocks to ensure at
least space for the ID exists. But a regular block should also have
at least 1 byte of data (otherwise it would be data-less instead of
regular).

Expand the get_data() block size sanity check to additionally expect
at least 1 byte of data.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Petr Mladek <pmladek@suse.com>
Link: https://patch.msgid.link/20260326133809.8045-2-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
master
John Ogness 2026-03-26 14:44:02 +01:06 committed by Petr Mladek
parent 8e81ecbf1c
commit 407f666db2
1 changed files with 5 additions and 2 deletions
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7
kernel/printk/printk_ringbuffer.c
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@ -1308,8 +1308,11 @@ static const char *get_data(struct prb_data_ring *data_ring,
return NULL;
}
/* A valid data block will always have at least an ID. */
if (WARN_ON_ONCE(*data_size < sizeof(db->id)))
/*
* A regular data block will always have an ID and at least
* 1 byte of data. Data-less blocks were handled earlier.
*/
if (WARN_ON_ONCE(*data_size <= sizeof(db->id)))
return NULL;
/* Subtract block ID space from size to reflect data size. */