Author: arekm Date: Wed Oct 20 17:33:28 2010 GMT Module: packages Tag: HEAD ---- Log message: - fix for http://seclists.org/bugtraq/2010/Oct/161
---- Files affected: packages/kernel: kernel-small_fixes.patch (1.9 -> 1.10) ---- Diffs: ================================================================ Index: packages/kernel/kernel-small_fixes.patch diff -u packages/kernel/kernel-small_fixes.patch:1.9 packages/kernel/kernel-small_fixes.patch:1.10 --- packages/kernel/kernel-small_fixes.patch:1.9 Sun Mar 7 14:30:30 2010 +++ packages/kernel/kernel-small_fixes.patch Wed Oct 20 19:33:23 2010 @@ -77,3 +77,81 @@ #include "../../include/linux/license.h" /* Some toolchains use a `_' prefix for all user symbols. */ +From 799c10559d60f159ab2232203f222f18fa3c4a5f Mon Sep 17 00:00:00 2001 +From: Linus Torvalds <[email protected]> +Date: Fri, 15 Oct 2010 11:09:28 -0700 +Subject: [PATCH] De-pessimize rds_page_copy_user + +Don't try to "optimize" rds_page_copy_user() by using kmap_atomic() and +the unsafe atomic user mode accessor functions. It's actually slower +than the straightforward code on any reasonable modern CPU. + +Back when the code was written (although probably not by the time it was +actually merged, though), 32-bit x86 may have been the dominant +architecture. And there kmap_atomic() can be a lot faster than kmap() +(unless you have very good locality, in which case the virtual address +caching by kmap() can overcome all the downsides). + +But these days, x86-64 may not be more populous, but it's getting there +(and if you care about performance, it's definitely already there - +you'd have upgraded your CPU's already in the last few years). And on +x86-64, the non-kmap_atomic() version is faster, simply because the code +is simpler and doesn't have the "re-try page fault" case. + +People with old hardware are not likely to care about RDS anyway, and +the optimization for the 32-bit case is simply buggy, since it doesn't +verify the user addresses properly. + +Reported-by: Dan Rosenberg <[email protected]> +Acked-by: Andrew Morton <[email protected]> +Cc: [email protected] +Signed-off-by: Linus Torvalds <[email protected]> +--- + net/rds/page.c | 27 +++++++-------------------- + 1 files changed, 7 insertions(+), 20 deletions(-) + +diff --git a/net/rds/page.c b/net/rds/page.c +index 595a952..1dfbfea 100644 +--- a/net/rds/page.c ++++ b/net/rds/page.c +@@ -57,30 +57,17 @@ int rds_page_copy_user(struct page *page, unsigned long offset, + unsigned long ret; + void *addr; + +- if (to_user) ++ addr = kmap(page); ++ if (to_user) { + rds_stats_add(s_copy_to_user, bytes); +- else ++ ret = copy_to_user(ptr, addr + offset, bytes); ++ } else { + rds_stats_add(s_copy_from_user, bytes); +- +- addr = kmap_atomic(page, KM_USER0); +- if (to_user) +- ret = __copy_to_user_inatomic(ptr, addr + offset, bytes); +- else +- ret = __copy_from_user_inatomic(addr + offset, ptr, bytes); +- kunmap_atomic(addr, KM_USER0); +- +- if (ret) { +- addr = kmap(page); +- if (to_user) +- ret = copy_to_user(ptr, addr + offset, bytes); +- else +- ret = copy_from_user(addr + offset, ptr, bytes); +- kunmap(page); +- if (ret) +- return -EFAULT; ++ ret = copy_from_user(addr + offset, ptr, bytes); + } ++ kunmap(page); + +- return 0; ++ return ret ? -EFAULT : 0; + } + EXPORT_SYMBOL_GPL(rds_page_copy_user); + +-- +1.7.3.1 + ================================================================ ---- CVS-web: http://cvs.pld-linux.org/cgi-bin/cvsweb.cgi/packages/kernel/kernel-small_fixes.patch?r1=1.9&r2=1.10&f=u _______________________________________________ pld-cvs-commit mailing list [email protected] http://lists.pld-linux.org/mailman/listinfo/pld-cvs-commit
