> 2023年9月6日 09:22，Rand Deeb <rand.sec96@xxxxxxxxx> 写道： > > In SHOW(), the variable 'n' is of type 'size_t.' While there is a > conditional check to verify that 'n' is not equal to zero before > executing the 'do_div' macro, concerns arise regarding potential > division by zero error in 64-bit environments. > > The concern arises when 'n' is 64 bits in size, greater than zero, and > the lower 32 bits of it are zeros. In such cases, the conditional check > passes because 'n' is non-zero, but the 'do_div' macro casts 'n' to > 'uint32_t,' effectively truncating it to its lower 32 bits. > Consequently, the 'n' value becomes zero. > > To fix this potential division by zero error and ensure precise > division handling, this commit replaces the 'do_div' macro with > div64_u64(). div64_u64() is designed to work with 64-bit operands, > guaranteeing that division is performed correctly. > > This change enhances the robustness of the code, ensuring that division > operations yield accurate results in all scenarios, eliminating the > possibility of division by zero, and improving compatibility across > different 64-bit environments. > > Found by Linux Verification Center (linuxtesting.org) with SVACE. > > Signed-off-by: Rand Deeb <rand.sec96@xxxxxxxxx> Thanks, added into my for-next queue. Coly Li > --- > drivers/md/bcache/sysfs.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c > index 554e3afc9b68..ca3e2f000cd4 100644 > --- a/drivers/md/bcache/sysfs.c > +++ b/drivers/md/bcache/sysfs.c > @@ -1078,7 +1078,7 @@ SHOW(__bch_cache) > sum += INITIAL_PRIO - cached[i]; > > if (n) > - do_div(sum, n); > + sum = div64_u64(sum, n); > > for (i = 0; i < ARRAY_SIZE(q); i++) > q[i] = INITIAL_PRIO - cached[n * (i + 1) / > -- > 2.34.1 >
