path: root/mm/maccess.c
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2019-02-25Revert "x86/fault: BUG() when uaccess helpers fault on kernel addresses"Linus Torvalds
This reverts commit 9da3f2b74054406f87dff7101a569217ffceb29b. It was well-intentioned, but wrong. Overriding the exception tables for instructions for random reasons is just wrong, and that is what the new code did. It caused problems for tracing, and it caused problems for strncpy_from_user(), because the new checks made perfectly valid use cases break, rather than catch things that did bad things. Unchecked user space accesses are a problem, but that's not a reason to add invalid checks that then people have to work around with silly flags (in this case, that 'kernel_uaccess_faults_ok' flag, which is just an odd way to say "this commit was wrong" and was sprinked into random places to hide the wrongness). The real fix to unchecked user space accesses is to get rid of the special "let's not check __get_user() and __put_user() at all" logic. Make __{get|put}_user() be just aliases to the regular {get|put}_user() functions, and make it impossible to access user space without having the proper checks in places. The raison d'ĂȘtre of the special double-underscore versions used to be that the range check was expensive, and if you did multiple user accesses, you'd do the range check up front (like the signal frame handling code, for example). But SMAP (on x86) and PAN (on ARM) have made that optimization pointless, because the _real_ expense is the "set CPU flag to allow user space access". Do let's not break the valid cases to catch invalid cases that shouldn't even exist. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Kees Cook <keescook@chromium.org> Cc: Tobin C. Harding <tobin@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Jann Horn <jannh@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-09-03x86/fault: BUG() when uaccess helpers fault on kernel addressesJann Horn
There have been multiple kernel vulnerabilities that permitted userspace to pass completely unchecked pointers through to userspace accessors: - the waitid() bug - commit 96ca579a1ecc ("waitid(): Add missing access_ok() checks") - the sg/bsg read/write APIs - the infiniband read/write APIs These don't happen all that often, but when they do happen, it is hard to test for them properly; and it is probably also hard to discover them with fuzzing. Even when an unmapped kernel address is supplied to such buggy code, it just returns -EFAULT instead of doing a proper BUG() or at least WARN(). Try to make such misbehaving code a bit more visible by refusing to do a fixup in the pagefault handler code when a userspace accessor causes a #PF on a kernel address and the current context isn't whitelisted. Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: kernel-hardening@lists.openwall.com Cc: dvyukov@google.com Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Cc: Borislav Petkov <bp@alien8.de> Link: https://lkml.kernel.org/r/20180828201421.157735-7-jannh@google.com
2018-02-06mm: docs: fix parameter names mismatchMike Rapoport
There are several places where parameter descriptions do no match the actual code. Fix it. Link: http://lkml.kernel.org/r/1516700871-22279-3-git-send-email-rppt@linux.vnet.ibm.com Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-22x86: remove more uaccess_32.h complexityLinus Torvalds
I'm looking at trying to possibly merge the 32-bit and 64-bit versions of the x86 uaccess.h implementation, but first this needs to be cleaned up. For example, the 32-bit version of "__copy_from_user_inatomic()" is mostly the special cases for the constant size, and it's actually almost never relevant. Most users aren't actually using a constant size anyway, and the few cases that do small constant copies are better off just using __get_user() instead. So get rid of the unnecessary complexity. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05mm/maccess.c: actually return -EFAULT from strncpy_from_unsafeRasmus Villemoes
As far as I can tell, strncpy_from_unsafe never returns -EFAULT. ret is the result of a __copy_from_user_inatomic(), which is 0 for success and positive (in this case necessarily 1) for access error - it is never negative. So we were always returning the length of the, possibly truncated, destination string. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Acked-by: Alexei Starovoitov <ast@kernel.org> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-05uaccess: reimplement probe_kernel_address() using probe_kernel_read()Andrew Morton
probe_kernel_address() is basically the same as the (later added) probe_kernel_read(). The return value on EFAULT is a bit different: probe_kernel_address() returns number-of-bytes-not-copied whereas probe_kernel_read() returns -EFAULT. All callers have been checked, none cared. probe_kernel_read() can be overridden by the architecture whereas probe_kernel_address() cannot. parisc, blackfin and um do this, to insert additional checking. Hence this patch possibly fixes obscure bugs, although there are only two probe_kernel_address() callsites outside arch/. My first attempt involved removing probe_kernel_address() entirely and converting all callsites to use probe_kernel_read() directly, but that got tiresome. This patch shrinks mm/slab_common.o by 218 bytes. For a single probe_kernel_address() callsite. Cc: Steven Miao <realmz6@gmail.com> Cc: Jeff Dike <jdike@addtoit.com> Cc: Richard Weinberger <richard@nod.at> Cc: "James E.J. Bottomley" <jejb@parisc-linux.org> Cc: Helge Deller <deller@gmx.de> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-08-31lib: move strncpy_from_unsafe() into mm/maccess.cAlexei Starovoitov
To fix build errors: kernel/built-in.o: In function `bpf_trace_printk': bpf_trace.c:(.text+0x11a254): undefined reference to `strncpy_from_unsafe' kernel/built-in.o: In function `fetch_memory_string': trace_kprobe.c:(.text+0x11acf8): undefined reference to `strncpy_from_unsafe' move strncpy_from_unsafe() next to probe_kernel_read/write() which use the same memory access style. Reported-by: Fengguang Wu <fengguang.wu@intel.com> Reported-by: Guenter Roeck <linux@roeck-us.net> Fixes: 1a6877b9c0c2 ("lib: introduce strncpy_from_unsafe()") Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-10-31mm: Map most files to use export.h instead of module.hPaul Gortmaker
The files changed within are only using the EXPORT_SYMBOL macro variants. They are not using core modular infrastructure and hence don't need module.h but only the export.h header. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
2011-05-25maccess,probe_kernel: Make write/read src const void *Steven Rostedt
The functions probe_kernel_write() and probe_kernel_read() do not modify the src pointer. Allow const pointers to be passed in without the need of a typecast. Acked-by: Mike Frysinger <vapier@gentoo.org> Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/1305824936.1465.4.camel@gandalf.stny.rr.com
2010-10-27MN10300: Save frame pointer in thread_info struct rather than global varDavid Howells
Save the current exception frame pointer in the thread_info struct rather than in a global variable as the latter makes SMP tricky, especially when preemption is also enabled. This also replaces __frame with current_frame() and rearranges header file inclusions to make it all compile. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
2010-01-07maccess,probe_kernel: Allow arch specific override probe_kernel_(read|write)Jason Wessel
Some archs such as blackfin, would like to have an arch specific probe_kernel_read() and probe_kernel_write() implementation which can fall back to the generic implementation if no special operations are needed. CC: Thomas Gleixner <tglx@linutronix.de> CC: Ingo Molnar <mingo@elte.hu> Signed-off-by: Jason Wessel <jason.wessel@windriver.com> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
2009-06-12[S390] maccess: add weak attribute to probe_kernel_writeHeiko Carstens
probe_kernel_write() gets used to write to the kernel address space. E.g. to patch the kernel (kgdb, ftrace, kprobes...). Some architectures however enable write protection for the kernel text section, so that writes to this region would fault. This patch allows to specify an architecture specific version of probe_kernel_write() which allows to handle and bypass write protection of the text segment. That way it is still possible to catch random writes to kernel text and explicitly allow writes via this interface. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2008-04-17kgdb: fix optional arch functions and probe_kernel_*Jason Wessel
Fix two regressions dealing with the kgdb core. 1) kgdb_skipexception and kgdb_post_primary_code are optional functions that are only required on archs that need special exception fixups. 2) The kernel address space scope must be set on any probe_kernel_* function or archs such as ARCH=arm will not allow access to the kernel memory space. As an example, it is required to allow the full kernel address space is when you the kernel debugger to inspect a system call. Signed-off-by: Jason Wessel <jason.wessel@windriver.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-04-17uaccess: add probe_kernel_write()Ingo Molnar
add probe_kernel_read() and probe_kernel_write(). Uninlined and restricted to kernel range memory only, as suggested by Linus. Signed-off-by: Ingo Molnar <mingo@elte.hu> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>