4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jiri Kosina <jkos...@suse.cz>
commit 39380b80d72723282f0ea1d1bbf2294eae45013e upstream.
Currently it's possible for broken (or malicious) userspace to flood a
kernel log indefinitely with messages a-la
Program dmidecode tried to access /dev/mem between f0000->100000
because range_is_allowed() is case of CONFIG_STRICT_DEVMEM being turned on
dumps this information each and every time devmem_is_allowed() fails.
Reportedly userspace that is able to trigger contignuous flow of these
messages exists.
It would be possible to rate limit this message, but that'd have a
questionable value; the administrator wouldn't get information about all
the failing accessess, so then the information would be both superfluous
and incomplete at the same time :)
Returning EPERM (which is what is actually happening) is enough indication
for userspace what has happened; no need to log this particular error as
some sort of special condition.
Signed-off-by: Jiri Kosina <jkos...@suse.cz>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Borislav Petkov <b...@alien8.de>
Cc: Brian Gerst <brge...@gmail.com>
Cc: Denys Vlasenko <dvlas...@redhat.com>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Josh Poimboeuf <jpoim...@redhat.com>
Cc: Kees Cook <keesc...@chromium.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Luis R. Rodriguez <mcg...@suse.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Toshi Kani <toshi.k...@hp.com>
Link: http://lkml.kernel.org/r/alpine.lnx.2.00.1607081137020.24...@cbobk.fhfr.pm
Signed-off-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/x86/mm/pat.c | 5 +----
drivers/char/mem.c | 6 +-----
2 files changed, 2 insertions(+), 9 deletions(-)
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -750,11 +750,8 @@ static inline int range_is_allowed(unsig
return 1;
while (cursor < to) {
- if (!devmem_is_allowed(pfn)) {
- pr_info("x86/PAT: Program %s tried to access /dev/mem
between [mem %#010Lx-%#010Lx], PAT prevents it\n",
- current->comm, from, to - 1);
+ if (!devmem_is_allowed(pfn))
return 0;
- }
cursor += PAGE_SIZE;
pfn++;
}
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -70,12 +70,8 @@ static inline int range_is_allowed(unsig
u64 cursor = from;
while (cursor < to) {
- if (!devmem_is_allowed(pfn)) {
- printk(KERN_INFO
- "Program %s tried to access /dev/mem between %Lx->%Lx.\n",
- current->comm, from, to);
+ if (!devmem_is_allowed(pfn))
return 0;
- }
cursor += PAGE_SIZE;
pfn++;
}
