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| author | Robin Murphy <robin.murphy@arm.com> | 2017-01-05 17:15:01 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-11 08:02:18 +0100 |
| commit | 488debb9971bc7d0edd6d8080ba78ca02a04f6c4 (patch) | |
| tree | 7f97b8edd11003152eefcd45345cb23fe617643e /drivers/char/mem.c | |
| parent | 7ee7f45a763bd68c3a606595a8c1bb08c3e6146b (diff) | |
| download | linux-488debb9971bc7d0edd6d8080ba78ca02a04f6c4.tar.gz linux-488debb9971bc7d0edd6d8080ba78ca02a04f6c4.tar.bz2 linux-488debb9971bc7d0edd6d8080ba78ca02a04f6c4.zip | |
drivers: char: mem: Fix thinkos in kmem address checks
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. Furthermore, do
so in the right place - a read or write may span multiple pages, so a
single up-front check is insufficient. High memory accesses already
have a similar validity check just before the copy_to_user() call, so
just make the low memory path fully consistent with that.
Reported-by: Jason A. Donenfeld <Jason@zx2c4.com>
CC: stable@vger.kernel.org
Fixes: 148a1bc84398 ("drivers: char: mem: Check {read,write}_kmem() addresses")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/char/mem.c')
| -rw-r--r-- | drivers/char/mem.c | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 5bb1985ec484..6d9cc2d39d22 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -381,9 +381,6 @@ 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; @@ -412,6 +409,8 @@ static ssize_t read_kmem(struct file *file, char __user *buf, * by the kernel or data corruption may occur */ kbuf = xlate_dev_kmem_ptr((void *)p); + if (!virt_addr_valid(kbuf)) + return -ENXIO; if (copy_to_user(buf, kbuf, sz)) return -EFAULT; @@ -482,6 +481,8 @@ static ssize_t do_write_kmem(unsigned long p, const char __user *buf, * corruption may occur. */ ptr = xlate_dev_kmem_ptr((void *)p); + if (!virt_addr_valid(ptr)) + return -ENXIO; copied = copy_from_user(ptr, buf, sz); if (copied) { @@ -512,9 +513,6 @@ 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); |