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| author | Will Deacon <will.deacon@arm.com> | 2014-06-02 11:47:23 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2014-06-18 12:40:57 +0100 |
| commit | c168870704bcde6bb63d05f7882b620dd3985a46 (patch) | |
| tree | 174f2ba42679903c0178f1a684adcad893e18b4e | |
| parent | 2d5a5612bceda8edd25b29f363c4e2c6cda28bab (diff) | |
| download | linux-c168870704bcde6bb63d05f7882b620dd3985a46.tar.bz2 | |
arm64: ptrace: change fs when passing kernel pointer to regset code
Our compat PTRACE_POKEUSR implementation simply passes the user data to
regset_copy_from_user after some simple range checking. Unfortunately,
the data in question has already been copied to the kernel stack by this
point, so the subsequent access_ok check fails and the ptrace request
returns -EFAULT. This causes problems tracing fork() with older versions
of strace.
This patch briefly changes the fs to KERNEL_DS, so that the access_ok
check passes even with a kernel address.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
| -rw-r--r-- | arch/arm64/kernel/ptrace.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 3e926b9c0641..993cdb79b70e 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -827,6 +827,7 @@ static int compat_ptrace_write_user(struct task_struct *tsk, compat_ulong_t off, compat_ulong_t val) { int ret; + mm_segment_t old_fs = get_fs(); if (off & 3 || off >= COMPAT_USER_SZ) return -EIO; @@ -834,10 +835,13 @@ static int compat_ptrace_write_user(struct task_struct *tsk, compat_ulong_t off, if (off >= sizeof(compat_elf_gregset_t)) return 0; + set_fs(KERNEL_DS); ret = copy_regset_from_user(tsk, &user_aarch32_view, REGSET_COMPAT_GPR, off, sizeof(compat_ulong_t), &val); + set_fs(old_fs); + return ret; } |