When borrowing the pfn_valid() check from mmap_kmem(), somebody managed to get physical and virtual addresses spectacularly muddled up, such that we've ended up with checks for one being the other. Whilst this does indeed prevent out-of-bounds accesses crashing, on most systems it also prevents the more desirable use-case of working at all ever.
Check the *virtual* offset correctly for what it is. Reported-by: Jason A. Donenfeld <[email protected]> CC: [email protected] Fixes: 148a1bc84398 ("drivers: char: mem: Check {read,write}_kmem() addresses") Signed-off-by: Robin Murphy <[email protected]> --- drivers/char/mem.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 5bb1985ec484..bdc6a4018604 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -381,7 +381,7 @@ static ssize_t read_kmem(struct file *file, char __user *buf, char *kbuf; /* k-addr because vread() takes vmlist_lock rwlock */ int err = 0; - if (!pfn_valid(PFN_DOWN(p))) + if (!virt_addr_valid(p)) return -EIO; read = 0; @@ -512,7 +512,7 @@ static ssize_t write_kmem(struct file *file, const char __user *buf, char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */ int err = 0; - if (!pfn_valid(PFN_DOWN(p))) + if (!virt_addr_valid(p)) return -EIO; if (p < (unsigned long) high_memory) { -- 2.10.2.dirty
