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authorJason A. Donenfeld <Jason@zx2c4.com>2022-10-05 17:43:38 +0300
committerJason A. Donenfeld <Jason@zx2c4.com>2022-10-12 02:42:55 +0300
commit81895a65ec63ee1daec3255dc1a06675d2fbe915 (patch)
tree03703a64413a07bd4e6a171a449a8f18c760e21c /drivers/mtd
parentd465bff130bf4ca17b6980abe51164ace1e0cba4 (diff)
downloadlinux-81895a65ec63ee1daec3255dc1a06675d2fbe915.tar.xz
treewide: use prandom_u32_max() when possible, part 1
Rather than incurring a division or requesting too many random bytes for the given range, use the prandom_u32_max() function, which only takes the minimum required bytes from the RNG and avoids divisions. This was done mechanically with this coccinelle script: @basic@ expression E; type T; identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; typedef u64; @@ ( - ((T)get_random_u32() % (E)) + prandom_u32_max(E) | - ((T)get_random_u32() & ((E) - 1)) + prandom_u32_max(E * XXX_MAKE_SURE_E_IS_POW2) | - ((u64)(E) * get_random_u32() >> 32) + prandom_u32_max(E) | - ((T)get_random_u32() & ~PAGE_MASK) + prandom_u32_max(PAGE_SIZE) ) @multi_line@ identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; identifier RAND; expression E; @@ - RAND = get_random_u32(); ... when != RAND - RAND %= (E); + RAND = prandom_u32_max(E); // Find a potential literal @literal_mask@ expression LITERAL; type T; identifier get_random_u32 =~ "get_random_int|prandom_u32|get_random_u32"; position p; @@ ((T)get_random_u32()@p & (LITERAL)) // Add one to the literal. @script:python add_one@ literal << literal_mask.LITERAL; RESULT; @@ value = None if literal.startswith('0x'): value = int(literal, 16) elif literal[0] in '123456789': value = int(literal, 10) if value is None: print("I don't know how to handle %s" % (literal)) cocci.include_match(False) elif value == 2**32 - 1 or value == 2**31 - 1 or value == 2**24 - 1 or value == 2**16 - 1 or value == 2**8 - 1: print("Skipping 0x%x for cleanup elsewhere" % (value)) cocci.include_match(False) elif value & (value + 1) != 0: print("Skipping 0x%x because it's not a power of two minus one" % (value)) cocci.include_match(False) elif literal.startswith('0x'): coccinelle.RESULT = cocci.make_expr("0x%x" % (value + 1)) else: coccinelle.RESULT = cocci.make_expr("%d" % (value + 1)) // Replace the literal mask with the calculated result. @plus_one@ expression literal_mask.LITERAL; position literal_mask.p; expression add_one.RESULT; identifier FUNC; @@ - (FUNC()@p & (LITERAL)) + prandom_u32_max(RESULT) @collapse_ret@ type T; identifier VAR; expression E; @@ { - T VAR; - VAR = (E); - return VAR; + return E; } @drop_var@ type T; identifier VAR; @@ { - T VAR; ... when != VAR } Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: Kees Cook <keescook@chromium.org> Reviewed-by: Yury Norov <yury.norov@gmail.com> Reviewed-by: KP Singh <kpsingh@kernel.org> Reviewed-by: Jan Kara <jack@suse.cz> # for ext4 and sbitmap Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@linbit.com> # for drbd Acked-by: Jakub Kicinski <kuba@kernel.org> Acked-by: Heiko Carstens <hca@linux.ibm.com> # for s390 Acked-by: Ulf Hansson <ulf.hansson@linaro.org> # for mmc Acked-by: Darrick J. Wong <djwong@kernel.org> # for xfs Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Diffstat (limited to 'drivers/mtd')
-rw-r--r--drivers/mtd/nand/raw/nandsim.c4
-rw-r--r--drivers/mtd/tests/mtd_nandecctest.c10
-rw-r--r--drivers/mtd/tests/stresstest.c17
-rw-r--r--drivers/mtd/ubi/debug.c2
-rw-r--r--drivers/mtd/ubi/debug.h6
5 files changed, 15 insertions, 24 deletions
diff --git a/drivers/mtd/nand/raw/nandsim.c b/drivers/mtd/nand/raw/nandsim.c
index 24beade95c7f..50bcf745e816 100644
--- a/drivers/mtd/nand/raw/nandsim.c
+++ b/drivers/mtd/nand/raw/nandsim.c
@@ -1405,9 +1405,9 @@ static void ns_do_bit_flips(struct nandsim *ns, int num)
if (bitflips && prandom_u32() < (1 << 22)) {
int flips = 1;
if (bitflips > 1)
- flips = (prandom_u32() % (int) bitflips) + 1;
+ flips = prandom_u32_max(bitflips) + 1;
while (flips--) {
- int pos = prandom_u32() % (num * 8);
+ int pos = prandom_u32_max(num * 8);
ns->buf.byte[pos / 8] ^= (1 << (pos % 8));
NS_WARN("read_page: flipping bit %d in page %d "
"reading from %d ecc: corrected=%u failed=%u\n",
diff --git a/drivers/mtd/tests/mtd_nandecctest.c b/drivers/mtd/tests/mtd_nandecctest.c
index c4f271314f52..1c7201b0f372 100644
--- a/drivers/mtd/tests/mtd_nandecctest.c
+++ b/drivers/mtd/tests/mtd_nandecctest.c
@@ -47,7 +47,7 @@ struct nand_ecc_test {
static void single_bit_error_data(void *error_data, void *correct_data,
size_t size)
{
- unsigned int offset = prandom_u32() % (size * BITS_PER_BYTE);
+ unsigned int offset = prandom_u32_max(size * BITS_PER_BYTE);
memcpy(error_data, correct_data, size);
__change_bit_le(offset, error_data);
@@ -58,9 +58,9 @@ static void double_bit_error_data(void *error_data, void *correct_data,
{
unsigned int offset[2];
- offset[0] = prandom_u32() % (size * BITS_PER_BYTE);
+ offset[0] = prandom_u32_max(size * BITS_PER_BYTE);
do {
- offset[1] = prandom_u32() % (size * BITS_PER_BYTE);
+ offset[1] = prandom_u32_max(size * BITS_PER_BYTE);
} while (offset[0] == offset[1]);
memcpy(error_data, correct_data, size);
@@ -71,7 +71,7 @@ static void double_bit_error_data(void *error_data, void *correct_data,
static unsigned int random_ecc_bit(size_t size)
{
- unsigned int offset = prandom_u32() % (3 * BITS_PER_BYTE);
+ unsigned int offset = prandom_u32_max(3 * BITS_PER_BYTE);
if (size == 256) {
/*
@@ -79,7 +79,7 @@ static unsigned int random_ecc_bit(size_t size)
* and 17th bit) in ECC code for 256 byte data block
*/
while (offset == 16 || offset == 17)
- offset = prandom_u32() % (3 * BITS_PER_BYTE);
+ offset = prandom_u32_max(3 * BITS_PER_BYTE);
}
return offset;
diff --git a/drivers/mtd/tests/stresstest.c b/drivers/mtd/tests/stresstest.c
index cb29c8c1b370..d2faaca7f19d 100644
--- a/drivers/mtd/tests/stresstest.c
+++ b/drivers/mtd/tests/stresstest.c
@@ -45,9 +45,8 @@ static int rand_eb(void)
unsigned int eb;
again:
- eb = prandom_u32();
/* Read or write up 2 eraseblocks at a time - hence 'ebcnt - 1' */
- eb %= (ebcnt - 1);
+ eb = prandom_u32_max(ebcnt - 1);
if (bbt[eb])
goto again;
return eb;
@@ -55,20 +54,12 @@ again:
static int rand_offs(void)
{
- unsigned int offs;
-
- offs = prandom_u32();
- offs %= bufsize;
- return offs;
+ return prandom_u32_max(bufsize);
}
static int rand_len(int offs)
{
- unsigned int len;
-
- len = prandom_u32();
- len %= (bufsize - offs);
- return len;
+ return prandom_u32_max(bufsize - offs);
}
static int do_read(void)
@@ -127,7 +118,7 @@ static int do_write(void)
static int do_operation(void)
{
- if (prandom_u32() & 1)
+ if (prandom_u32_max(2))
return do_read();
else
return do_write();
diff --git a/drivers/mtd/ubi/debug.c b/drivers/mtd/ubi/debug.c
index 31d427ee191a..908d0e088557 100644
--- a/drivers/mtd/ubi/debug.c
+++ b/drivers/mtd/ubi/debug.c
@@ -590,7 +590,7 @@ int ubi_dbg_power_cut(struct ubi_device *ubi, int caller)
if (ubi->dbg.power_cut_max > ubi->dbg.power_cut_min) {
range = ubi->dbg.power_cut_max - ubi->dbg.power_cut_min;
- ubi->dbg.power_cut_counter += prandom_u32() % range;
+ ubi->dbg.power_cut_counter += prandom_u32_max(range);
}
return 0;
}
diff --git a/drivers/mtd/ubi/debug.h b/drivers/mtd/ubi/debug.h
index 118248a5d7d4..dc8d8f83657a 100644
--- a/drivers/mtd/ubi/debug.h
+++ b/drivers/mtd/ubi/debug.h
@@ -73,7 +73,7 @@ static inline int ubi_dbg_is_bgt_disabled(const struct ubi_device *ubi)
static inline int ubi_dbg_is_bitflip(const struct ubi_device *ubi)
{
if (ubi->dbg.emulate_bitflips)
- return !(prandom_u32() % 200);
+ return !prandom_u32_max(200);
return 0;
}
@@ -87,7 +87,7 @@ static inline int ubi_dbg_is_bitflip(const struct ubi_device *ubi)
static inline int ubi_dbg_is_write_failure(const struct ubi_device *ubi)
{
if (ubi->dbg.emulate_io_failures)
- return !(prandom_u32() % 500);
+ return !prandom_u32_max(500);
return 0;
}
@@ -101,7 +101,7 @@ static inline int ubi_dbg_is_write_failure(const struct ubi_device *ubi)
static inline int ubi_dbg_is_erase_failure(const struct ubi_device *ubi)
{
if (ubi->dbg.emulate_io_failures)
- return !(prandom_u32() % 400);
+ return !prandom_u32_max(400);
return 0;
}