@matheusbsbs / matheus-bagliano / commits / 1fbb8d7ecb

builtin/blame: fix out-of-bounds read with excessive `--abbrev`

In 6411a0a896 (builtin/blame: fix type of `length` variable when emitting object ID, 2024-12-06) we have fixed the type of the `length` variable. In order to avoid a cast from `size_t` to `int` in the call to printf(3p) with the "%.*s" formatter we have converted the code to instead use fwrite(3p), which accepts the length as a `size_t`. It was reported though that this makes us read over the end of the OID array when the provided `--abbrev=` length exceeds the length of the object ID. This is because fwrite(3p) of course doesn't stop when it sees a NUL byte, whereas printf(3p) does. Fix the bug by reverting back to printf(3p) and culling the provided length to `GIT_MAX_HEXSZ` to keep it from overflowing when cast to an `int`. Reported-by: Johannes Schindelin <Johannes.Schindelin@gmx.de> Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Patrick Steinhardt committed Jan 10, 2025 at 12:26 UTC 1fbb8d7ecb7bd78ac55d226b6b073372a5ea2c2d

2 files changed +10 -1

builtin/blame.c

+2 -1

@@ -505,7 +505,8 @@ static void emit_other(struct blame_scoreboard *sb, struct blame_entry *ent, int

505 length--;

506 putchar('?');

507 }

508 - fwrite(hex, 1, length, stdout);

508 +

509 + printf("%.*s", (int)(length < GIT_MAX_HEXSZ ? length : GIT_MAX_HEXSZ), hex);

510 if (opt & OUTPUT_ANNOTATE_COMPAT) {

511 const char *name;

512 if (opt & OUTPUT_SHOW_EMAIL)

t/t8002-blame.sh

@@ -126,6 +126,14 @@ test_expect_success '--no-abbrev works like --abbrev with full length' '

126 check_abbrev $hexsz --no-abbrev

127 '

128

129 +test_expect_success 'blame --abbrev gets truncated' '

130 + check_abbrev $hexsz --abbrev=9000 HEAD

131 +'

132 +

133 +test_expect_success 'blame --abbrev gets truncated with boundary commit' '

134 + check_abbrev $hexsz --abbrev=9000 ^HEAD

135 +'

136 +

137 test_expect_success '--exclude-promisor-objects does not BUG-crash' '

138 test_must_fail git blame --exclude-promisor-objects one

139 '