diff mbox series

[bpf,v2,1/2] bpf, xdp: clean head/meta when expanding it

Message ID 20250331032354.75808-2-jiayuan.chen@linux.dev (mailing list archive)
State New
Delegated to: BPF
Headers show
Series bpf, xdp: clean adjust_{head,meta} memory when offset < 0 | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf, async
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present fail Series targets non-next tree, but doesn't contain any Fixes tags
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 467 this patch: 467
netdev/build_tools fail Errors and warnings before: 26 (+0) this patch: 27 (+0)
netdev/cc_maintainers success CCed 19 of 19 maintainers
netdev/build_clang success Errors and warnings before: 924 this patch: 924
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 16023 this patch: 16023
netdev/checkpatch warning WARNING: The commit message has 'syzkaller', perhaps it also needs a 'Fixes:' tag?
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 6 this patch: 6
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-PR success PR summary
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bpf/vmtest-bpf-VM_Test-51 success Logs for x86_64-llvm-18 / veristat-meta
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bpf/vmtest-bpf-VM_Test-44 success Logs for x86_64-llvm-18 / build-release / build for x86_64 with llvm-18-O2
bpf/vmtest-bpf-VM_Test-40 success Logs for x86_64-llvm-17 / veristat-kernel
bpf/vmtest-bpf-VM_Test-31 success Logs for x86_64-gcc / veristat-kernel / x86_64-gcc veristat_kernel
bpf/vmtest-bpf-VM_Test-41 success Logs for x86_64-llvm-17 / veristat-meta
bpf/vmtest-bpf-VM_Test-43 success Logs for x86_64-llvm-18 / build / build for x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-34 success Logs for x86_64-llvm-17 / build / build for x86_64 with llvm-17
bpf/vmtest-bpf-VM_Test-18 success Logs for s390x-gcc / test (test_verifier, false, 360) / test_verifier on s390x with gcc
bpf/vmtest-bpf-VM_Test-22 success Logs for x86_64-gcc / GCC BPF / GCC BPF
bpf/vmtest-bpf-VM_Test-25 success Logs for x86_64-gcc / test (test_maps, false, 360) / test_maps on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-27 success Logs for x86_64-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-32 success Logs for x86_64-gcc / veristat-meta / x86_64-gcc veristat_meta
bpf/vmtest-bpf-VM_Test-28 success Logs for x86_64-gcc / test (test_progs_no_alu32_parallel, true, 30) / test_progs_no_alu32_parallel on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-30 success Logs for x86_64-gcc / test (test_verifier, false, 360) / test_verifier on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-29 success Logs for x86_64-gcc / test (test_progs_parallel, true, 30) / test_progs_parallel on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-33 success Logs for x86_64-llvm-17 / GCC BPF / GCC BPF
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bpf/vmtest-bpf-VM_Test-49 success Logs for x86_64-llvm-18 / test (test_verifier, false, 360) / test_verifier on x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-39 success Logs for x86_64-llvm-17 / test (test_verifier, false, 360) / test_verifier on x86_64 with llvm-17
bpf/vmtest-bpf-VM_Test-36 success Logs for x86_64-llvm-17 / test (test_maps, false, 360) / test_maps on x86_64 with llvm-17
bpf/vmtest-bpf-VM_Test-26 success Logs for x86_64-gcc / test (test_progs, false, 360) / test_progs on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-9 success Logs for aarch64-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-45 success Logs for x86_64-llvm-18 / test (test_maps, false, 360) / test_maps on x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-47 success Logs for x86_64-llvm-18 / test (test_progs_cpuv4, false, 360) / test_progs_cpuv4 on x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-46 success Logs for x86_64-llvm-18 / test (test_progs, false, 360) / test_progs on x86_64 with llvm-18
bpf/vmtest-bpf-VM_Test-38 success Logs for x86_64-llvm-17 / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with llvm-17
bpf/vmtest-bpf-VM_Test-37 success Logs for x86_64-llvm-17 / test (test_progs, false, 360) / test_progs on x86_64 with llvm-17
bpf/vmtest-bpf-VM_Test-8 success Logs for aarch64-gcc / test (test_progs, false, 360) / test_progs on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-48 success Logs for x86_64-llvm-18 / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with llvm-18

Commit Message

Jiayuan Chen March 31, 2025, 3:23 a.m. UTC 
The device allocates an skb, it additionally allocates a prepad size
(usually equal to NET_SKB_PAD or XDP_PACKET_HEADROOM) but leaves it
uninitialized.

The bpf_xdp_adjust_head function moves skb->data forward, which allows
users to access data belonging to other programs, posing a security risk.

Reported-by: syzbot+0e6ddb1ef80986bdfe64@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/00000000000067f65105edbd295d@google.com/T/
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
---
 include/uapi/linux/bpf.h       | 8 +++++---
 net/core/filter.c              | 5 ++++-
 tools/include/uapi/linux/bpf.h | 6 ++++--
 3 files changed, 13 insertions(+), 6 deletions(-)
diff mbox series

Patch

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index defa5bb881f4..be01a848cbbf 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2760,8 +2760,9 @@  union bpf_attr {
  *
  * long bpf_xdp_adjust_head(struct xdp_buff *xdp_md, int delta)
  * 	Description
- * 		Adjust (move) *xdp_md*\ **->data** by *delta* bytes. Note that
- * 		it is possible to use a negative value for *delta*. This helper
+ *		Adjust (move) *xdp_md*\ **->data** by *delta* bytes. Note that
+ *		it is possible to use a negative value for *delta*. If *delta*
+ *		is negative, the new header will be memset to zero. This helper
  * 		can be used to prepare the packet for pushing or popping
  * 		headers.
  *
@@ -2989,7 +2990,8 @@  union bpf_attr {
  * long bpf_xdp_adjust_meta(struct xdp_buff *xdp_md, int delta)
  * 	Description
  * 		Adjust the address pointed by *xdp_md*\ **->data_meta** by
- * 		*delta* (which can be positive or negative). Note that this
+ *		*delta* (which can be positive or negative). If *delta* is
+ *		negative, the new meta will be memset to zero. Note that this
  * 		operation modifies the address stored in *xdp_md*\ **->data**,
  * 		so the latter must be loaded only after the helper has been
  * 		called.
diff --git a/net/core/filter.c b/net/core/filter.c
index 46ae8eb7a03c..5f01d373b719 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3947,6 +3947,8 @@  BPF_CALL_2(bpf_xdp_adjust_head, struct xdp_buff *, xdp, int, offset)
 	if (metalen)
 		memmove(xdp->data_meta + offset,
 			xdp->data_meta, metalen);
+	if (offset < 0)
+		memset(data, 0, -offset);
 	xdp->data_meta += offset;
 	xdp->data = data;
 
@@ -4239,7 +4241,8 @@  BPF_CALL_2(bpf_xdp_adjust_meta, struct xdp_buff *, xdp, int, offset)
 		return -EINVAL;
 	if (unlikely(xdp_metalen_invalid(metalen)))
 		return -EACCES;
-
+	if (offset < 0)
+		memset(meta, 0, -offset);
 	xdp->data_meta = meta;
 
 	return 0;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index defa5bb881f4..7b1871f2eccf 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -2761,7 +2761,8 @@  union bpf_attr {
  * long bpf_xdp_adjust_head(struct xdp_buff *xdp_md, int delta)
  * 	Description
  * 		Adjust (move) *xdp_md*\ **->data** by *delta* bytes. Note that
- * 		it is possible to use a negative value for *delta*. This helper
+ *		it is possible to use a negative value for *delta*. If *delta*
+ *		is negative, the new header will be memset to zero. This helper
  * 		can be used to prepare the packet for pushing or popping
  * 		headers.
  *
@@ -2989,7 +2990,8 @@  union bpf_attr {
  * long bpf_xdp_adjust_meta(struct xdp_buff *xdp_md, int delta)
  * 	Description
  * 		Adjust the address pointed by *xdp_md*\ **->data_meta** by
- * 		*delta* (which can be positive or negative). Note that this
+ *		*delta* (which can be positive or negative). If *delta* is
+ *		negative, the new meta will be memset to zero. Note that this
  * 		operation modifies the address stored in *xdp_md*\ **->data**,
  * 		so the latter must be loaded only after the helper has been
  * 		called.