diff options
| author | Robin Murphy <robin.murphy@arm.com> | 2016-06-01 19:21:42 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-08-31 15:21:18 +0200 |
| commit | 148a1bc84398039e2b96ff78678c4d9a67f81452 (patch) | |
| tree | 7c477963ee32e086a8d374b70b0015b93ffc5601 /drivers/char | |
| parent | d61f3088ea79c1f11fc8fe869d6f90a4cc97a452 (diff) | |
drivers: char: mem: Check {read,write}_kmem() addresses
Arriving at read_kmem() with an offset representing a bogus kernel
address (e.g. 0 from a simple "cat /dev/kmem") leads to copy_to_user
faulting on the kernel-side read.
x86_64 happens to get away with this since the optimised implementation
uses "rep movs*", thus the user write (which is allowed to fault) and
the kernel read are the same instruction, the kernel-side fault falls
into the user-side fixup handler and the chain of events which
transpires ends up returning an error as one might expect, even if it's
an inappropriate -EFAULT. On other architectures, though, the read is
not covered by the fixup entry for the write, and we get a big scary
"Unable to hande kernel paging request..." dump.
The more typical use-case of mmap_kmem() has always (within living
memory at least) returned -EIO for addresses which don't satisfy
pfn_valid(), so let's make that consistent across {read,write}_kem()
too.
Reported-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/char')
| -rw-r--r-- | drivers/char/mem.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index a33163dbb913..5bb1985ec484 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -381,6 +381,9 @@ 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))) + return -EIO; + read = 0; if (p < (unsigned long) high_memory) { low_count = count; @@ -509,6 +512,9 @@ 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))) + return -EIO; + if (p < (unsigned long) high_memory) { unsigned long to_write = min_t(unsigned long, count, (unsigned long)high_memory - p); |