Public bug reported: == SRU Justification == Impacts all releases from Trusty through Yakkety
http://paste.ubuntu.com/23309548/ >From ca47910e3b549501b6a3ff786174d2f0d4748ccf Mon Sep 17 00:00:00 2001 From: Paul Mackerras <[email protected]> Date: Tue, 11 Oct 2016 22:18:58 +1100 Subject: [PATCH] powerpc/64: Fix incorrect return value from__copy_tofrom_user Debugging a data corruption issue with virtio-net/vhost-net led to the observation that __copy_tofrom_user was occasionally returning a value 16 larger than it should. Since the return value from __copy_tofrom_user is the number of bytes not copied, this means that __copy_tofrom_user can occasionally return a value larger than the number of bytes it was asked to copy. In turn this can cause higher-level copy functions such as copy_page_to_iter_iovec to corrupt memory by copying data into the wrong memory locations. It turns out that the failing case involves a fault on the store at label 79, and at that point the first unmodified byte of the destination is at R3 + 16. Consequently the exception handler for that store needs to add 16 to R3 before using it to work out how many bytes were not copied, but in this one case it was not adding the offset to R3. To fix it, this moves the label 179 to the point where we add 16 to R3. I have checked manually all the exception handlers for the loads and stores in this code and the rest of them are correct (it would be excellent to have an automated test of all the exception cases). Signed-off-by: Paul Mackerras <[email protected]> --- arch/powerpc/lib/copyuser_64.S | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/lib/copyuser_64.S b/arch/powerpc/lib/copyuser_64.S index f09899e..7b22624 100644 --- a/arch/powerpc/lib/copyuser_64.S +++ b/arch/powerpc/lib/copyuser_64.S @@ -359,6 +359,7 @@ END_FTR_SECTION_IFCLR(CPU_FTR_UNALIGNED_LD_STD) addi r3,r3,8 171: 177: +179: addi r3,r3,8 370: 372: @@ -373,7 +374,6 @@ END_FTR_SECTION_IFCLR(CPU_FTR_UNALIGNED_LD_STD) 173: 174: 175: -179: 181: 184: 186: -- 2.7.4 ** Affects: linux (Ubuntu) Importance: Undecided Status: Incomplete ** Tags: trusty -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1632462 Title: [Trusty->Yakkety] powerpc/64: Fix incorrect return value from __copy_tofrom_user To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1632462/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
