diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h index 9f2839e73f8a..f5a350347bc5 100644 --- a/include/linux/seq_buf.h +++ b/include/linux/seq_buf.h @@ -155,11 +155,11 @@ static inline void seq_buf_commit(struct seq_buf *s, int num) * * Removes the last written character to the seq_buf @s. * - * Returns the last character or -1 if it is empty. + * Returns the last character, or -1 if @s is empty or has overflowed. */ static inline int seq_buf_pop(struct seq_buf *s) { - if (!s->len) + if (!s->len || seq_buf_has_overflowed(s)) return -1; s->len--; diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h index 697d619aafdc..7174ebf3f015 100644 --- a/include/linux/trace_seq.h +++ b/include/linux/trace_seq.h @@ -86,7 +86,10 @@ static inline bool trace_seq_has_overflowed(struct trace_seq *s) * * Removes the last written character to the trace_seq @s. * - * Returns the last character or -1 if it is empty. + * Returns the last character, or -1 if the underlying seq_buf is empty or + * has overflowed. Note that only that buffer is consulted: a @s marked + * full by a write that did not fit, which trace_seq_has_overflowed() + * reports as overflowed, still pops the last character written. */ static inline int trace_seq_pop(struct trace_seq *s) { diff --git a/lib/tests/seq_buf_kunit.c b/lib/tests/seq_buf_kunit.c index 0934dfb602ff..de491f96c1ac 100644 --- a/lib/tests/seq_buf_kunit.c +++ b/lib/tests/seq_buf_kunit.c @@ -115,6 +115,47 @@ static void seq_buf_putc_test(struct kunit *test) KUNIT_EXPECT_STREQ(test, seq_buf_str(&s), ""); } +static void seq_buf_pop_test(struct kunit *test) +{ + DECLARE_SEQ_BUF(s, 8); + struct seq_buf t; + char *buf; + + /* Nothing to pop. */ + KUNIT_EXPECT_EQ(test, seq_buf_pop(&s), -1); + KUNIT_EXPECT_EQ(test, s.len, 0); + + seq_buf_puts(&s, "hello"); + KUNIT_EXPECT_EQ(test, seq_buf_pop(&s), 'o'); + KUNIT_EXPECT_EQ(test, seq_buf_used(&s), 4); + KUNIT_EXPECT_STREQ(test, seq_buf_str(&s), "hell"); + + /* A 0xff byte must not be mistaken for an empty buffer. */ + seq_buf_putc(&s, 0xff); + KUNIT_EXPECT_EQ(test, seq_buf_pop(&s), 0xff); + + /* A full buffer pops its last byte. */ + seq_buf_puts(&s, "abc"); + seq_buf_putc(&s, 'd'); + KUNIT_EXPECT_FALSE(test, seq_buf_has_overflowed(&s)); + KUNIT_EXPECT_EQ(test, seq_buf_used(&s), 8); + KUNIT_EXPECT_EQ(test, seq_buf_pop(&s), 'd'); + KUNIT_EXPECT_EQ(test, seq_buf_used(&s), 7); + KUNIT_EXPECT_STREQ(test, seq_buf_str(&s), "hellabc"); + + /* + * An overflowed buffer has nothing to pop, and stays overflowed. Use + * a buffer allocated at its exact size, so that KASAN reports any + * read past its end. + */ + buf = kunit_kmalloc(test, 16, GFP_KERNEL); + KUNIT_ASSERT_NOT_NULL(test, buf); + seq_buf_init(&t, buf, 16); + KUNIT_EXPECT_EQ(test, seq_buf_printf(&t, "%s", "longer than sixteen"), -1); + KUNIT_EXPECT_EQ(test, seq_buf_pop(&t), -1); + KUNIT_EXPECT_TRUE(test, seq_buf_has_overflowed(&t)); +} + static void seq_buf_printf_test(struct kunit *test) { DECLARE_SEQ_BUF(s, 32); @@ -354,6 +395,7 @@ static struct kunit_case seq_buf_test_cases[] = { KUNIT_CASE(seq_buf_puts_test), KUNIT_CASE(seq_buf_puts_overflow_test), KUNIT_CASE(seq_buf_putc_test), + KUNIT_CASE(seq_buf_pop_test), KUNIT_CASE(seq_buf_printf_test), KUNIT_CASE(seq_buf_printf_overflow_test), KUNIT_CASE(seq_buf_get_buf_commit_test),