In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
bpf, arm64: set up the frame pointer for the exception callback<\/p>\n
A program acting as exception boundary saves all callee-saved registers,
\nso build_prologue() takes the exception_cb path and never calls
\npush_callee_regs(). That is the only place find_used_callee_regs() runs,
\nand with it the only place ctx->fp_used is set, so the callback prologue
\ndoes not emit the<\/p>\n
mov x25, sp<\/p>\n
that points BPF_REG_FP at the frame the callback runs on. x25 keeps
\nwhatever it held when bpf_throw() was called. If the throw came from a
\nsubprogram that uses its own BPF stack, that is the subprogram’s frame
\npointer, and since the subprogram never returns it never restores x25
\neither.<\/p>\n
Stack accesses through BPF_REG_FP are rewritten to be stack pointer
\nrelative, so those still land in the callback’s own frame. Materializing
\nthe register does not: a callback that passes the address of a local
\nvariable to a helper hands over an address in the dead subprogram’s
\nframe. That address is below the callback’s stack pointer by then, and
\nthe helper’s own call chain covers it, so the helper can write over its
\nown return address. 0x1234 below is the value the helper was asked to
\nstore:<\/p>\n
pc : 0x1234
\n lr : 0x1234
\n Call trace:
\n 0x1234 (P)
\n bpf_test_run+0x188\/0x3e0
\n bpf_prog_test_run_skb+0x47c\/0x998
\n __sys_bpf+0xbdc\/0xdd8
\n Kernel panic – not syncing: Oops: Fatal exception in interrupt<\/p>\n
Set ctx->fp_used on the exception callback path so that the existing code
\nfurther down sets x25 from the stack pointer. The epilogue restores it
\nfrom the main program’s save area along with the other callee-saved
\nregisters, as it already does. x86 sets the frame pointer for the
\ncallback from the argument it is passed, and powerpc computes it from
\nthe stack pointer.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
bpf, arm64: set up the frame pointer for the exception callback<\/p>\n
A program acting as exception boundary saves all callee-saved regi<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-41113","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/41113","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=41113"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=41113"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=41113"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}