libbpf: bound /proc/<pid>/maps scansets in parse_vma_segs()#12152
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libbpf: bound /proc/<pid>/maps scansets in parse_vma_segs()#12152kernel-patches-daemon-bpf[bot] wants to merge 1 commit into
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parse_vma_segs() in tools/lib/bpf/usdt.c parses /proc/<pid>/maps
with two widthless scansets, "%s" into mode[16] and "%[^\n]"
into line[PATH_MAX]. Both assume the kernel caps maps records
to PATH_MAX, but it does not.
show_map_vma() emits the path via seq_path() against the seq
buffer, which doubles on overflow (m->size <<= 1 in
fs/seq_file.c), so a VMA whose backing path is a deeply nested
directory tree produces a single maps record longer than
PATH_MAX. scanf "%s" / "%[^\n]" without a width writes until
the field terminator regardless of destination size, so a
bpf_program__attach_usdt() consumer attaching against
an attacker-controlled PID overflows its own stack inside
parse_vma_segs().
Bound both scansets to the declared buffer sizes ("%15s" for
mode[16] and "%4095[^\n]" for line[PATH_MAX]) and drain any
residue past line[4094] with "%*[^\n]" before the trailing "\n",
matching the libbpf-local fscanf style. Without the drain the
residue of an over-long record would stay in the stream and
break the next "%zx-%zx" parse, so the loop would exit early and
any maps records after the over-long entry would be silently
skipped.
Fixes: 3e6fe5c ("libbpf: Fix internal USDT address translation logic for shared libraries")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Author
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Upstream branch: b1fcdf9 |
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Pull request for series with
subject: libbpf: bound /proc//maps scansets in parse_vma_segs()
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1099035