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Among the existing architecture specific versions of copy_siginfo_to_user32 there are several different implementation problems. Some architectures fail to handle all of the cases in in the siginfo union. Some architectures perform a blind copy of the siginfo union when the si_code is negative. A blind copy suggests the data is expected to be in 32bit siginfo format, which means that receiving such a signal via signalfd won't work, or that the data is in 64bit siginfo and the code is copying nonsense to userspace. Create a single instance of copy_siginfo_to_user32 that all of the architectures can share, and teach it to handle all of the cases in the siginfo union correctly, with the assumption that siginfo is stored internally to the kernel is 64bit siginfo format. A special case is made for x86 x32 format. This is needed as presence of both x32 and ia32 on x86_64 results in two different 32bit signal formats. By allowing this small special case there winds up being exactly one code base that needs to be maintained between all of the architectures. Vastly increasing the testing base and the chances of finding bugs. As the x86 copy of copy_siginfo_to_user32 the call of the x86 signal_compat_build_tests were moved into sigaction_compat_abi, so that they will keep running. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
118 lines
3.7 KiB
C
118 lines
3.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/compat.h>
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#include <linux/uaccess.h>
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#include <linux/ptrace.h>
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/*
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* The compat_siginfo_t structure and handing code is very easy
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* to break in several ways. It must always be updated when new
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* updates are made to the main siginfo_t, and
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* copy_siginfo_to_user32() must be updated when the
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* (arch-independent) copy_siginfo_to_user() is updated.
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*
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* It is also easy to put a new member in the compat_siginfo_t
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* which has implicit alignment which can move internal structure
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* alignment around breaking the ABI. This can happen if you,
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* for instance, put a plain 64-bit value in there.
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*/
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static inline void signal_compat_build_tests(void)
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{
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int _sifields_offset = offsetof(compat_siginfo_t, _sifields);
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/*
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* If adding a new si_code, there is probably new data in
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* the siginfo. Make sure folks bumping the si_code
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* limits also have to look at this code. Make sure any
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* new fields are handled in copy_siginfo_to_user32()!
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*/
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BUILD_BUG_ON(NSIGILL != 11);
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BUILD_BUG_ON(NSIGFPE != 13);
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BUILD_BUG_ON(NSIGSEGV != 4);
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BUILD_BUG_ON(NSIGBUS != 5);
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BUILD_BUG_ON(NSIGTRAP != 4);
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BUILD_BUG_ON(NSIGCHLD != 6);
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BUILD_BUG_ON(NSIGSYS != 1);
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/* This is part of the ABI and can never change in size: */
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BUILD_BUG_ON(sizeof(compat_siginfo_t) != 128);
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/*
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* The offsets of all the (unioned) si_fields are fixed
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* in the ABI, of course. Make sure none of them ever
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* move and are always at the beginning:
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*/
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BUILD_BUG_ON(offsetof(compat_siginfo_t, _sifields) != 3 * sizeof(int));
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#define CHECK_CSI_OFFSET(name) BUILD_BUG_ON(_sifields_offset != offsetof(compat_siginfo_t, _sifields.name))
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/*
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* Ensure that the size of each si_field never changes.
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* If it does, it is a sign that the
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* copy_siginfo_to_user32() code below needs to updated
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* along with the size in the CHECK_SI_SIZE().
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*
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* We repeat this check for both the generic and compat
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* siginfos.
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*
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* Note: it is OK for these to grow as long as the whole
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* structure stays within the padding size (checked
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* above).
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*/
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#define CHECK_CSI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((compat_siginfo_t *)0)->_sifields.name))
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#define CHECK_SI_SIZE(name, size) BUILD_BUG_ON(size != sizeof(((siginfo_t *)0)->_sifields.name))
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CHECK_CSI_OFFSET(_kill);
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CHECK_CSI_SIZE (_kill, 2*sizeof(int));
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CHECK_SI_SIZE (_kill, 2*sizeof(int));
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CHECK_CSI_OFFSET(_timer);
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CHECK_CSI_SIZE (_timer, 3*sizeof(int));
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CHECK_SI_SIZE (_timer, 6*sizeof(int));
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CHECK_CSI_OFFSET(_rt);
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CHECK_CSI_SIZE (_rt, 3*sizeof(int));
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CHECK_SI_SIZE (_rt, 4*sizeof(int));
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CHECK_CSI_OFFSET(_sigchld);
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CHECK_CSI_SIZE (_sigchld, 5*sizeof(int));
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CHECK_SI_SIZE (_sigchld, 8*sizeof(int));
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#ifdef CONFIG_X86_X32_ABI
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CHECK_CSI_OFFSET(_sigchld_x32);
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CHECK_CSI_SIZE (_sigchld_x32, 7*sizeof(int));
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/* no _sigchld_x32 in the generic siginfo_t */
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#endif
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CHECK_CSI_OFFSET(_sigfault);
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CHECK_CSI_SIZE (_sigfault, 4*sizeof(int));
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CHECK_SI_SIZE (_sigfault, 8*sizeof(int));
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CHECK_CSI_OFFSET(_sigpoll);
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CHECK_CSI_SIZE (_sigpoll, 2*sizeof(int));
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CHECK_SI_SIZE (_sigpoll, 4*sizeof(int));
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CHECK_CSI_OFFSET(_sigsys);
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CHECK_CSI_SIZE (_sigsys, 3*sizeof(int));
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CHECK_SI_SIZE (_sigsys, 4*sizeof(int));
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/* any new si_fields should be added here */
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}
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void sigaction_compat_abi(struct k_sigaction *act, struct k_sigaction *oact)
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{
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signal_compat_build_tests();
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/* Don't leak in-kernel non-uapi flags to user-space */
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if (oact)
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oact->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
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if (!act)
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return;
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/* Don't let flags to be set from userspace */
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act->sa.sa_flags &= ~(SA_IA32_ABI | SA_X32_ABI);
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if (in_ia32_syscall())
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act->sa.sa_flags |= SA_IA32_ABI;
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if (in_x32_syscall())
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act->sa.sa_flags |= SA_X32_ABI;
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}
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