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bpf: fix panic in stack_map_get_build_id() on i386 and arm32

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[ Upstream commit beaf3d1901 ]

As Naresh reported, test_stacktrace_build_id() causes panic on i386 and
arm32 systems. This is caused by page_address() returns NULL in certain
cases.

This patch fixes this error by using kmap_atomic/kunmap_atomic instead
of page_address.

Fixes: 615755a77b (" bpf: extend stackmap to save binary_build_id+offset instead of address")
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Song Liu 2019-01-08 14:20:44 -08:00 • committed by Greg Kroah-Hartman
commit 2f3480e340
1 changed files with 2 additions and 1 deletions
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3
kernel/bpf/stackmap.c
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@ -260,7 +260,7 @@ static int stack_map_get_build_id(struct vm_area_struct *vma,
return -EFAULT; /* page not mapped */
ret = -EINVAL;
page_addr = page_address(page);
page_addr = kmap_atomic(page);
ehdr = (Elf32_Ehdr *)page_addr;
/* compare magic x7f "ELF" */
@ -276,6 +276,7 @@ static int stack_map_get_build_id(struct vm_area_struct *vma,
else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
ret = stack_map_get_build_id_64(page_addr, build_id);
out:
kunmap_atomic(page_addr);
put_page(page);
return ret;
}