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| author | Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> | 2021-05-19 13:47:17 +0300 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-05-28 14:52:42 +0300 |
| commit | 82123a3d1d5a306fdf50c968a474cc60fe43a80f (patch) | |
| tree | 0bc27b73514fbcbcff456603cd3148d3474ba097 /arch/powerpc | |
| parent | d72500f992849d31ebae8f821a023660ddd0dcc2 (diff) | |
| download | linux-82123a3d1d5a306fdf50c968a474cc60fe43a80f.tar.xz | |
powerpc/kprobes: Fix validation of prefixed instructions across page boundary
When checking if the probed instruction is the suffix of a prefixed
instruction, we access the instruction at the previous word. If the
probed instruction is the very first word of a module, we can end up
trying to access an invalid page.
Fix this by skipping the check for all instructions at the beginning of
a page. Prefixed instructions cannot cross a 64-byte boundary and as
such, we don't expect to encounter a suffix as the very first word in a
page for kernel text. Even if there are prefixed instructions crossing
a page boundary (from a module, for instance), the instruction will be
illegal, so preventing probing on the suffix of such prefix instructions
isn't worthwhile.
Fixes: b4657f7650ba ("powerpc/kprobes: Don't allow breakpoints on suffixes")
Cc: stable@vger.kernel.org # v5.8+
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/0df9a032a05576a2fa8e97d1b769af2ff0eafbd6.1621416666.git.naveen.n.rao@linux.vnet.ibm.com
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/kernel/kprobes.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c index 01ab2163659e..e8c2a6373157 100644 --- a/arch/powerpc/kernel/kprobes.c +++ b/arch/powerpc/kernel/kprobes.c @@ -108,7 +108,6 @@ int arch_prepare_kprobe(struct kprobe *p) int ret = 0; struct kprobe *prev; struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->addr); - struct ppc_inst prefix = ppc_inst_read((struct ppc_inst *)(p->addr - 1)); if ((unsigned long)p->addr & 0x03) { printk("Attempt to register kprobe at an unaligned address\n"); @@ -116,7 +115,8 @@ int arch_prepare_kprobe(struct kprobe *p) } else if (IS_MTMSRD(insn) || IS_RFID(insn) || IS_RFI(insn)) { printk("Cannot register a kprobe on rfi/rfid or mtmsr[d]\n"); ret = -EINVAL; - } else if (ppc_inst_prefixed(prefix)) { + } else if ((unsigned long)p->addr & ~PAGE_MASK && + ppc_inst_prefixed(ppc_inst_read((struct ppc_inst *)(p->addr - 1)))) { printk("Cannot register a kprobe on the second word of prefixed instruction\n"); ret = -EINVAL; } |