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2015-01-22x86, tls: Interpret an all-zero struct user_desc as "no segment"Andy Lutomirski
The Witcher 2 did something like this to allocate a TLS segment index: struct user_desc u_info; bzero(&u_info, sizeof(u_info)); u_info.entry_number = (uint32_t)-1; syscall(SYS_set_thread_area, &u_info); Strictly speaking, this code was never correct. It should have set read_exec_only and seg_not_present to 1 to indicate that it wanted to find a free slot without putting anything there, or it should have put something sensible in the TLS slot if it wanted to allocate a TLS entry for real. The actual effect of this code was to allocate a bogus segment that could be used to exploit espfix. The set_thread_area hardening patches changed the behavior, causing set_thread_area to return -EINVAL and crashing the game. This changes set_thread_area to interpret this as a request to find a free slot and to leave it empty, which isn't *quite* what the game expects but should be close enough to keep it working. In particular, using the code above to allocate two segments will allocate the same segment both times. According to FrostbittenKing on Github, this fixes The Witcher 2. If this somehow still causes problems, we could instead allocate a limit==0 32-bit data segment, but that seems rather ugly to me. Fixes: 41bdc78544b8 x86/tls: Validate TLS entries to protect espfix Signed-off-by: Andy Lutomirski <luto@amacapital.net> Cc: stable@vger.kernel.org Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/0cb251abe1ff0958b8e468a9a9a905b80ae3a746.1421954363.git.luto@amacapital.net Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-12-18x86/tls: Don't validate lm in set_thread_area() after allAndy Lutomirski
It turns out that there's a lurking ABI issue. GCC, when compiling this in a 32-bit program: struct user_desc desc = { .entry_number = idx, .base_addr = base, .limit = 0xfffff, .seg_32bit = 1, .contents = 0, /* Data, grow-up */ .read_exec_only = 0, .limit_in_pages = 1, .seg_not_present = 0, .useable = 0, }; will leave .lm uninitialized. This means that anything in the kernel that reads user_desc.lm for 32-bit tasks is unreliable. Revert the .lm check in set_thread_area(). The value never did anything in the first place. Fixes: 0e58af4e1d21 ("x86/tls: Disallow unusual TLS segments") Signed-off-by: Andy Lutomirski <luto@amacapital.net> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org # Only if 0e58af4e1d21 is backported Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/d7875b60e28c512f6a6fc0baf5714d58e7eaadbb.1418856405.git.luto@amacapital.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-12-14x86/tls: Disallow unusual TLS segmentsAndy Lutomirski
Users have no business installing custom code segments into the GDT, and segments that are not present but are otherwise valid are a historical source of interesting attacks. For completeness, block attempts to set the L bit. (Prior to this patch, the L bit would have been silently dropped.) This is an ABI break. I've checked glibc, musl, and Wine, and none of them look like they'll have any trouble. Note to stable maintainers: this is a hardening patch that fixes no known bugs. Given the possibility of ABI issues, this probably shouldn't be backported quickly. Signed-off-by: Andy Lutomirski <luto@amacapital.net> Acked-by: H. Peter Anvin <hpa@zytor.com> Cc: stable@vger.kernel.org # optional Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: security@kernel.org <security@kernel.org> Cc: Willy Tarreau <w@1wt.eu> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2014-12-14x86/tls: Validate TLS entries to protect espfixAndy Lutomirski
Installing a 16-bit RW data segment into the GDT defeats espfix. AFAICT this will not affect glibc, Wine, or dosemu at all. Signed-off-by: Andy Lutomirski <luto@amacapital.net> Acked-by: H. Peter Anvin <hpa@zytor.com> Cc: stable@vger.kernel.org Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: security@kernel.org <security@kernel.org> Cc: Willy Tarreau <w@1wt.eu> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2013-03-03make SYSCALL_DEFINE<n>-generated wrappers do asmlinkage_protectAl Viro
... and switch i386 to HAVE_SYSCALL_WRAPPERS, killing open-coded uses of asmlinkage_protect() in a bunch of syscalls. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-03-29Merge branch 'x86-urgent-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86 updates from Ingo Molnar. This touches some non-x86 files due to the sanitized INLINE_SPIN_UNLOCK config usage. Fixed up trivial conflicts due to just header include changes (removing headers due to cpu_idle() merge clashing with the <asm/system.h> split). * 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/apic/amd: Be more verbose about LVT offset assignments x86, tls: Off by one limit check x86/ioapic: Add io_apic_ops driver layer to allow interception x86/olpc: Add debugfs interface for EC commands x86: Merge the x86_32 and x86_64 cpu_idle() functions x86/kconfig: Remove CONFIG_TR=y from the defconfigs x86: Stop recursive fault in print_context_stack after stack overflow x86/io_apic: Move and reenable irq only when CONFIG_GENERIC_PENDING_IRQ=y x86/apic: Add separate apic_id_valid() functions for selected apic drivers locking/kconfig: Simplify INLINE_SPIN_UNLOCK usage x86/kconfig: Update defconfigs x86: Fix excessive MSR print out when show_msr is not specified
2012-03-28Disintegrate asm/system.h for X86David Howells
Disintegrate asm/system.h for X86. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: H. Peter Anvin <hpa@zytor.com> cc: x86@kernel.org
2012-03-28x86, tls: Off by one limit checkDan Carpenter
These are used as offsets into an array of GDT_ENTRY_TLS_ENTRIES members so GDT_ENTRY_TLS_ENTRIES is one past the end of the array. Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Link: http://lkml.kernel.org/r/20120324075250.GA28258@elgon.mountain Cc: <stable@vger.kernel.org> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
2008-07-22x86: Introducing asm/syscalls.hJaswinder Singh
Declaring arch-dependent syscalls for x86 architecture Signed-off-by: Jaswinder Singh <jaswinder@infradead.org>
2008-04-10asmlinkage_protect replaces prevent_tail_callRoland McGrath
The prevent_tail_call() macro works around the problem of the compiler clobbering argument words on the stack, which for asmlinkage functions is the caller's (user's) struct pt_regs. The tail/sibling-call optimization is not the only way that the compiler can decide to use stack argument words as scratch space, which we have to prevent. Other optimizations can do it too. Until we have new compiler support to make "asmlinkage" binding on the compiler's own use of the stack argument frame, we have work around all the manifestations of this issue that crop up. More cases seem to be prevented by also keeping the incoming argument variables live at the end of the function. This makes their original stack slots attractive places to leave those variables, so the compiler tends not clobber them for something else. It's still no guarantee, but it handles some observed cases that prevent_tail_call() did not. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-29x86: tls prevent_tail_callRoland McGrath
Fix a kernel bug (vmware boot problem) reported by Tomasz Grobelny, which occurs with certain .config variants and gccs. The x86 TLS cleanup in commit efd1ca52d04d2f6df337a3332cee56cd60e6d4c4 made the sys_set_thread_area and sys_get_thread_area functions ripe for tail call optimization. If the compiler chooses to use it for them, it can clobber the user trap frame because these are asmlinkage functions. Reported-by: Tomasz Grobelny <tomasz@grobelny.oswiecenia.net> Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-01-30x86: x86 user_regset TLSRoland McGrath
This adds accessor functions in the user_regset style for the TLS data. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: x86 TLS desc_struct cleanupRoland McGrath
This cleans up the TLS code to use struct desc_struct and to separate the encoding and installation magic from the interface wrappers. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: modify get_desc_baseGlauber de Oliveira Costa
This patch makes get_desc_base() receive a struct desc_struct, and then uses its internal fields to compute the base address. This is done at both i386 and x86_64, and then it is moved to common header Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: introduce fill_ldtGlauber de Oliveira Costa
This patch introduces fill_ldt(), which populates a ldt descriptor from a user_desc in once, instead of relying in the LDT_entry_a and LDT_entry_b macros Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: TLS cleanupRoland McGrath
This consolidates the four different places that implemented the same encoding magic for the GDT-slot 32-bit TLS support. The old tls32.c was renamed and is now only slightly modified to be the shared implementation. Signed-off-by: Roland McGrath <roland@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Zachary Amsden <zach@vmware.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-01-30x86: tls32 movedRoland McGrath
This renames arch/x86/ia32/tls32.c to arch/x86/kernel/tls.c, which does nothing now but paves the way to consolidate this code for 32-bit too. Signed-off-by: Roland McGrath <roland@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Zachary Amsden <zach@vmware.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>