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From b45833f10556483f80abf1a239fff7712d0555dd Mon Sep 17 00:00:00 2001 |
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From: Will Deacon <will.deacon@arm.com> |
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Date: Wed, 5 Sep 2018 15:34:42 +0100 |
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Subject: [PATCH 041/145] signal: Introduce COMPAT_SIGMINSTKSZ for use in |
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compat_sys_sigaltstack |
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|
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[ Upstream commit 22839869f21ab3850fbbac9b425ccc4c0023926f ] |
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|
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The sigaltstack(2) system call fails with -ENOMEM if the new alternative |
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signal stack is found to be smaller than SIGMINSTKSZ. On architectures |
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such as arm64, where the native value for SIGMINSTKSZ is larger than |
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the compat value, this can result in an unexpected error being reported |
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to a compat task. See, for example: |
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|
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https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=904385 |
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|
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This patch fixes the problem by extending do_sigaltstack to take the |
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minimum signal stack size as an additional parameter, allowing the |
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native and compat system call entry code to pass in their respective |
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values. COMPAT_SIGMINSTKSZ is just defined as SIGMINSTKSZ if it has not |
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been defined by the architecture. |
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|
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Cc: Arnd Bergmann <arnd@arndb.de> |
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Cc: Dominik Brodowski <linux@dominikbrodowski.net> |
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Cc: "Eric W. Biederman" <ebiederm@xmission.com> |
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Cc: Andrew Morton <akpm@linux-foundation.org> |
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Cc: Al Viro <viro@zeniv.linux.org.uk> |
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Cc: Oleg Nesterov <oleg@redhat.com> |
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Reported-by: Steve McIntyre <steve.mcintyre@arm.com> |
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Tested-by: Steve McIntyre <93sam@debian.org> |
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Signed-off-by: Will Deacon <will.deacon@arm.com> |
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Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> |
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Signed-off-by: Sasha Levin <sashal@kernel.org> |
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--- |
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include/linux/compat.h | 3 +++ |
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kernel/signal.c | 14 +++++++++----- |
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2 files changed, 12 insertions(+), 5 deletions(-) |
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|
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diff --git a/include/linux/compat.h b/include/linux/compat.h |
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index 1a3c4f37e908..de0c13bdcd2c 100644 |
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--- a/include/linux/compat.h |
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+++ b/include/linux/compat.h |
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@@ -103,6 +103,9 @@ typedef struct compat_sigaltstack { |
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compat_size_t ss_size; |
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} compat_stack_t; |
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#endif |
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+#ifndef COMPAT_MINSIGSTKSZ |
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+#define COMPAT_MINSIGSTKSZ MINSIGSTKSZ |
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+#endif |
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|
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#define compat_jiffies_to_clock_t(x) \ |
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(((unsigned long)(x) * COMPAT_USER_HZ) / HZ) |
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diff --git a/kernel/signal.c b/kernel/signal.c |
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index 5843c541fda9..e4aad0e90882 100644 |
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--- a/kernel/signal.c |
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+++ b/kernel/signal.c |
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@@ -3460,7 +3460,8 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact) |
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} |
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|
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static int |
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-do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp) |
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+do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp, |
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+ size_t min_ss_size) |
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{ |
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struct task_struct *t = current; |
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|
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@@ -3490,7 +3491,7 @@ do_sigaltstack (const stack_t *ss, stack_t *oss, unsigned long sp) |
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ss_size = 0; |
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ss_sp = NULL; |
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} else { |
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- if (unlikely(ss_size < MINSIGSTKSZ)) |
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+ if (unlikely(ss_size < min_ss_size)) |
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return -ENOMEM; |
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} |
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|
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@@ -3508,7 +3509,8 @@ SYSCALL_DEFINE2(sigaltstack,const stack_t __user *,uss, stack_t __user *,uoss) |
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if (uss && copy_from_user(&new, uss, sizeof(stack_t))) |
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return -EFAULT; |
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err = do_sigaltstack(uss ? &new : NULL, uoss ? &old : NULL, |
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- current_user_stack_pointer()); |
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+ current_user_stack_pointer(), |
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+ MINSIGSTKSZ); |
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if (!err && uoss && copy_to_user(uoss, &old, sizeof(stack_t))) |
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err = -EFAULT; |
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return err; |
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@@ -3519,7 +3521,8 @@ int restore_altstack(const stack_t __user *uss) |
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stack_t new; |
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if (copy_from_user(&new, uss, sizeof(stack_t))) |
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return -EFAULT; |
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- (void)do_sigaltstack(&new, NULL, current_user_stack_pointer()); |
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+ (void)do_sigaltstack(&new, NULL, current_user_stack_pointer(), |
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+ MINSIGSTKSZ); |
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/* squash all but EFAULT for now */ |
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return 0; |
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} |
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@@ -3553,7 +3556,8 @@ static int do_compat_sigaltstack(const compat_stack_t __user *uss_ptr, |
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uss.ss_size = uss32.ss_size; |
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} |
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ret = do_sigaltstack(uss_ptr ? &uss : NULL, &uoss, |
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- compat_user_stack_pointer()); |
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+ compat_user_stack_pointer(), |
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+ COMPAT_MINSIGSTKSZ); |
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if (ret >= 0 && uoss_ptr) { |
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compat_stack_t old; |
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memset(&old, 0, sizeof(old)); |
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-- |
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2.19.1 |
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