Commit-ID: 39380b80d72723282f0ea1d1bbf2294eae45013e
Gitweb: http://git.kernel.org/tip/39380b80d72723282f0ea1d1bbf2294eae45013e
Author: Jiri Kosina <jkosina@xxxxxxx>
AuthorDate: Fri, 8 Jul 2016 11:38:28 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 8 Jul 2016 11:52:58 +0200
x86/mm/pat, /dev/mem: Remove superfluous error message
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 <jkosina@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Luis R. Rodriguez <mcgrof@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Toshi Kani <toshi.kani@xxxxxx>
Link: http://lkml.kernel.org/r/alpine.LNX.2.00.1607081137020.24757@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/mm/pat.c | 5 +----
drivers/char/mem.c | 6 +-----
2 files changed, 2 insertions(+), 9 deletions(-)
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index fb0604f..db00e3e 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -755,11 +755,8 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size)
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++;
}
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 71025c2..d633974 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -66,12 +66,8 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size)
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++;
}
--
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