https://github.com/torvalds/linux
Revision 4954f5b8ef0baf70fe978d1a99a5f70e4dd5c877 authored by Joerg Roedel on 19 May 2021, 13:52:46 UTC, committed by Borislav Petkov on 19 May 2021, 16:45:37 UTC
The put_user() and get_user() functions do checks on the address which is passed to them. They check whether the address is actually a user-space address and whether its fine to access it. They also call might_fault() to indicate that they could fault and possibly sleep. All of these checks are neither wanted nor needed in the #VC exception handler, which can be invoked from almost any context and also for MMIO instructions from kernel space on kernel memory. All the #VC handler wants to know is whether a fault happened when the access was tried. This is provided by __put_user()/__get_user(), which just do the access no matter what. Also add comments explaining why __get_user() and __put_user() are the best choice here and why it is safe to use them in this context. Also explain why copy_to/from_user can't be used. In addition, also revert commit 7024f60d6552 ("x86/sev-es: Handle string port IO to kernel memory properly") because using __get_user()/__put_user() fixes the same problem while the above commit introduced several problems: 1) It uses access_ok() which is only allowed in task context. 2) It uses memcpy() which has no fault handling at all and is thus unsafe to use here. [ bp: Fix up commit ID of the reverted commit above. ] Fixes: f980f9c31a92 ("x86/sev-es: Compile early handler code into kernel image") Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: stable@vger.kernel.org # v5.10+ Link: https://lkml.kernel.org/r/20210519135251.30093-4-joro@8bytes.org
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Tip revision: 4954f5b8ef0baf70fe978d1a99a5f70e4dd5c877 authored by Joerg Roedel on 19 May 2021, 13:52:46 UTC
x86/sev-es: Use __put_user()/__get_user() for data accesses
x86/sev-es: Use __put_user()/__get_user() for data accesses
Tip revision: 4954f5b
File | Mode | Size |
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LICENSES | ||
arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.clang-format | -rw-r--r-- | 16.4 KB |
.cocciconfig | -rw-r--r-- | 59 bytes |
.get_maintainer.ignore | -rw-r--r-- | 71 bytes |
.gitattributes | -rw-r--r-- | 62 bytes |
.gitignore | -rw-r--r-- | 1.9 KB |
.mailmap | -rw-r--r-- | 19.4 KB |
COPYING | -rw-r--r-- | 496 bytes |
CREDITS | -rw-r--r-- | 98.6 KB |
Kbuild | -rw-r--r-- | 1.3 KB |
Kconfig | -rw-r--r-- | 555 bytes |
MAINTAINERS | -rw-r--r-- | 587.9 KB |
Makefile | -rw-r--r-- | 64.2 KB |
README | -rw-r--r-- | 727 bytes |
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