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From 9348ded117d05ba1d54a748173db009d473c707c Mon Sep 17 00:00:00 2001
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From: Andrea Claudi <aclaudi@redhat.com>
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Date: Thu, 13 Jun 2019 14:37:57 +0200
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Subject: [PATCH] bpf: initialise map symbol before retrieving and comparing
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its type
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1716361
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Upstream Status: iproute2.git commit 1a7d3ad8a5862
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commit 1a7d3ad8a5862ca9ce9dd19326faeea77e5e6142
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Author: Quentin Monnet <quentin.monnet@netronome.com>
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Date: Tue Nov 20 01:26:27 2018 +0000
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bpf: initialise map symbol before retrieving and comparing its type
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In order to compare BPF map symbol type correctly in regard to the
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latest LLVM, commit 7a04dd84a7f9 ("bpf: check map symbol type properly
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with newer llvm compiler") compares map symbol type to both NOTYPE and
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OBJECT. To do so, it first retrieves the type from "sym.st_info" and
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stores it into a temporary variable.
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However, the type is collected from the symbol "sym" before this latter
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symbol is actually updated. gelf_getsym() is called after that and
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updates "sym", and when comparison with OBJECT or NOTYPE happens it is
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done on the type of the symbol collected in the previous passage of the
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loop (or on an uninitialised symbol on the first passage). This may
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eventually break map collection from the ELF file.
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Fix this by assigning the type to the temporary variable only after the
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call to gelf_getsym().
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Fixes: 7a04dd84a7f9 ("bpf: check map symbol type properly with newer llvm compiler")
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Reported-by: Ron Philip <ron.philip@netronome.com>
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Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
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Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
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Acked-by: Yonghong Song <yhs@fb.com>
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Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
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---
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lib/bpf.c | 10 +++++++---
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1 file changed, 7 insertions(+), 3 deletions(-)
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diff --git a/lib/bpf.c b/lib/bpf.c
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index 45f279fa4a416..6aff8f7bad7fb 100644
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--- a/lib/bpf.c
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+++ b/lib/bpf.c
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@@ -1758,11 +1758,12 @@ static const char *bpf_map_fetch_name(struct bpf_elf_ctx *ctx, int which)
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int i;
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for (i = 0; i < ctx->sym_num; i++) {
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- int type = GELF_ST_TYPE(sym.st_info);
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+ int type;
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if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym)
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continue;
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+ type = GELF_ST_TYPE(sym.st_info);
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if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL ||
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(type != STT_NOTYPE && type != STT_OBJECT) ||
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sym.st_shndx != ctx->sec_maps ||
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@@ -1851,11 +1852,12 @@ static int bpf_map_num_sym(struct bpf_elf_ctx *ctx)
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GElf_Sym sym;
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for (i = 0; i < ctx->sym_num; i++) {
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- int type = GELF_ST_TYPE(sym.st_info);
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+ int type;
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if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym)
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continue;
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+ type = GELF_ST_TYPE(sym.st_info);
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if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL ||
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(type != STT_NOTYPE && type != STT_OBJECT) ||
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sym.st_shndx != ctx->sec_maps)
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@@ -1931,10 +1933,12 @@ static int bpf_map_verify_all_offs(struct bpf_elf_ctx *ctx, int end)
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* the table again.
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*/
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for (i = 0; i < ctx->sym_num; i++) {
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- int type = GELF_ST_TYPE(sym.st_info);
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+ int type;
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if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym)
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continue;
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+
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+ type = GELF_ST_TYPE(sym.st_info);
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if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL ||
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(type != STT_NOTYPE && type != STT_OBJECT) ||
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sym.st_shndx != ctx->sec_maps)
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--
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2.20.1
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