A vulnerability was found in the Linux kernel in the bpf_enum_value_kind() function, where a lack of proper checks could lead to an uninitialized variable being used. This issue could lead to undefined behavior or memory corruption.
In the Linux kernel, the following vulnerability has been resolved:
bpf: Avoid uninitialized value in BPF_CORE_READ_BITFIELD
[Changes from V1:
- Use a default branch in the switch statement to initialize `val'.]
GCC warns that `val' may be used uninitialized in the
BPF_CRE_READ_BITFIELD macro, defined in bpf_core_read.h as:
[...]
unsigned long long val; \
[...] \
switch (__CORE_RELO(s, field, BYTE_SIZE)) { \
case 1: val = *(const unsigned char *)p; break; \
case 2: val = *(const unsigned short *)p; break; \
case 4: val = *(const unsigned int *)p; break; \
case 8: val = *(const unsigned long long *)p; break; \
} \
[...]
val; \
} \
This patch adds a default entry in the switch statement that sets
`val' to zero in order to avoid the warning, and random values to be
used in case __builtin_preserve_field_info returns unexpected values
for BPF_FIELD_BYTE_SIZE.
Tested in bpf-next master.
No regressions.
Comment 1Mauro Matteo Cascella
2024-07-31 11:30:19 UTC
In the Linux kernel, the following vulnerability has been resolved: bpf: Avoid uninitialized value in BPF_CORE_READ_BITFIELD [Changes from V1: - Use a default branch in the switch statement to initialize `val'.] GCC warns that `val' may be used uninitialized in the BPF_CRE_READ_BITFIELD macro, defined in bpf_core_read.h as: [...] unsigned long long val; \ [...] \ switch (__CORE_RELO(s, field, BYTE_SIZE)) { \ case 1: val = *(const unsigned char *)p; break; \ case 2: val = *(const unsigned short *)p; break; \ case 4: val = *(const unsigned int *)p; break; \ case 8: val = *(const unsigned long long *)p; break; \ } \ [...] val; \ } \ This patch adds a default entry in the switch statement that sets `val' to zero in order to avoid the warning, and random values to be used in case __builtin_preserve_field_info returns unexpected values for BPF_FIELD_BYTE_SIZE. Tested in bpf-next master. No regressions.