Callers of copy_from_user() expect it to return the number of bytes
it could not copy. In no case it is supposed to return -EFAULT.
In case of a detected buffer overflow just return the requested
length. In addition one could think of a memset that would clear
the size of the target object.
[ hpa: code is not in .32 so not needed for -stable ]
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
LKML-Reference: <20100105131911.GC5480@osiris.boeblingen.de.ibm.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
In order to avoid unnecessary chains of branches, rather than
implementing copy_user_generic() as a function consisting of
just a single (possibly patched) branch, instead properly deal
with patching call instructions in the alternative instructions
framework, and move the patching into the callers.
As a follow-on, one could also introduce something like
__EXPORT_SYMBOL_ALT() to avoid patching call sites in modules.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <4B2BB8180200007800026AE7@vpn.id2.novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
On x86-64, copy_[to|from]_user() rely on assembly routines that
never call might_fault(), making us missing various lockdep
checks.
This doesn't apply to __copy_from,to_user() that explicitly
handle these calls, neither is it a problem in x86-32 where
copy_to,from_user() rely on the "__" prefixed versions that
also call might_fault().
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1258382538-30979-1-git-send-email-fweisbec@gmail.com>
[ v2: fix module export ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This v2.6.26 commit:
ad2fc2c: x86: fix copy_user on x86
rendered __copy_from_user_inatomic() identical to
copy_user_generic(), yet didn't make the former just call the
latter from an inline function.
Furthermore, this v2.6.19 commit:
b885808: [PATCH] Add proper sparse __user casts to __copy_to_user_inatomic
converted the return type of __copy_to_user_inatomic() from
unsigned long to int, but didn't do the same to
__copy_from_user_inatomic().
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: <v.mayatskih@gmail.com>
LKML-Reference: <4AFD5778020000780001F8F4@vpn.id2.novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
gcc (4.x) supports the __builtin_object_size() builtin, which
reports the size of an object that a pointer point to, when known
at compile time. If the buffer size is not known at compile time, a
constant -1 is returned.
This patch uses this feature to add a sanity check to
copy_from_user(); if the target buffer is known to be smaller than
the copy size, the copy is aborted and a WARNing is emitted in
memory debug mode.
These extra checks compile away when the object size is not known,
or if both the buffer size and the copy length are constants.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
LKML-Reference: <20090926143301.2c396b94@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
arch/x86/include/asm/uaccess_64.h uses wrong asm operand constraint
("ir") for movq insn. Since movq sign-extends its immediate operand,
"er" constraint should be used instead.
Attached patch changes all uses of __put_user_asm in uaccess_64.h to use
"er" when "q" insn suffix is involved.
Patch was compile tested on x86_64 with defconfig.
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: stable@kernel.org
Impact: standardize IO on cached ops
On modern CPUs it is almost always a bad idea to use non-temporal stores,
as the regression in this commit has shown it:
30d697f: x86: fix performance regression in write() syscall
The kernel simply has no good information about whether using non-temporal
stores is a good idea or not - and trying to add heuristics only increases
complexity and inserts fragility.
The regression on cached write()s took very long to be found - over two
years. So dont take any chances and let the hardware decide how it makes
use of its caches.
The only exception is drivers/gpu/drm/i915/i915_gem.c: there were we are
absolutely sure that another entity (the GPU) will pick up the dirty
data immediately and that the CPU will not touch that data before the
GPU will.
Also, keep the _nocache() primitives to make it easier for people to
experiment with these details. There may be more clear-cut cases where
non-cached copies can be used, outside of filemap.c.
Cc: Salman Qazi <sqazi@google.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: make more types of copies non-temporal
This change makes the following simple fix:
30d697f: x86: fix performance regression in write() syscall
A bit more sophisticated: we check the 'total' number of bytes
written to decide whether to copy in a cached or a non-temporal
way.
This will for example cause the tail (modulo 4096 bytes) chunk
of a large write() to be non-temporal too - not just the page-sized
chunks.
Cc: Salman Qazi <sqazi@google.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: cleanup, enable future change
Add a 'total bytes copied' parameter to __copy_from_user_*nocache(),
and update all the callsites.
The parameter is not used yet - architecture code can use it to
more intelligently decide whether the copy should be cached or
non-temporal.
Cc: Salman Qazi <sqazi@google.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
While the introduction of __copy_from_user_nocache (see commit:
0812a579c9) may have been an improvement
for sufficiently large writes, there is evidence to show that it is
deterimental for small writes. Unixbench's fstime test gives the
following results for 256 byte writes with MAX_BLOCK of 2000:
2.6.29-rc6 ( 5 samples, each in KB/sec ):
283750, 295200, 294500, 293000, 293300
2.6.29-rc6 + this patch (5 samples, each in KB/sec):
313050, 3106750, 293350, 306300, 307900
2.6.18
395700, 342000, 399100, 366050, 359850
See w_test() in src/fstime.c in unixbench version 4.1.0. Basically, the above test
consists of counting how much we can write in this manner:
alarm(10);
while (!sigalarm) {
for (f_blocks = 0; f_blocks < 2000; ++f_blocks) {
write(f, buf, 256);
}
lseek(f, 0L, 0);
}
Note, there are other components to the write syscall regression
that are not addressed here.
Signed-off-by: Salman Qazi <sqazi@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
__copy_from_user() will return invalid value 16 when it fails to
access user space and the size is 10.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Change header guards named "ASM_X86__*" to "_ASM_X86_*" since:
a. the double underscore is ugly and pointless.
b. no leading underscore violates namespace constraints.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Linus Torvalds