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libbpf: Fix invalid write loop logic in bpf_linker__add_buf() 

Fix bpf_linker__add_buf()'s logic of copying data from memory buffer into
memfd. In the event of short write not writing entire buf_sz bytes into memfd
file, we'll append bytes from the beginning of buf *again* (corrupting ELF
file contents) instead of correctly appending the rest of not-yet-read buf
contents.

Closes: https://github.com/libbpf/libbpf/issues/945
Fixes: 6d5e5e5d7c ("libbpf: Extend linker API to support in-memory ELF files")
Signed-off-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20260209230134.3530521-1-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Amery Hung 2026-02-09 15:01:34 -08:00 committed by Alexei Starovoitov
parent 728ff16791
commit 04999b99e8
1 changed files with 1 additions and 1 deletions
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tools/lib/bpf/linker.c
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@ -581,7 +581,7 @@ int bpf_linker__add_buf(struct bpf_linker *linker, void *buf, size_t buf_sz,
written = 0;
while (written < buf_sz) {
ret = write(fd, buf, buf_sz);
ret = write(fd, buf + written, buf_sz - written);
if (ret < 0) {
ret = -errno;
pr_warn("failed to write '%s': %s\n", filename, errstr(ret));