TLS 1.3 started using the entry at the end of the SG array for chaining-in the single byte content type entry. This mostly works: [ E E E E E E . . ] ^ ^ start end E < content type / [ E E E E E E C . ] ^ ^ start end (Where E denotes a populated SG entry; C denotes a chaining entry.) If the array is full, however, the end will point to the start: [ E E E E E E E E ] ^ start end And we end up overwriting the start: E < content type / [ C E E E E E E E ] ^ start end The sg array is supposed to be a circular buffer with start and end markers pointing anywhere. In case where start > end (i.e. the circular buffer has "wrapped") there is an extra entry reserved at the end to chain the two halves together. [ E E E E E E . . l ] (Where l is the reserved entry for "looping" back to front. As suggested by John, let's reserve another entry for chaining SG entries after the main circular buffer. Note that this entry has to be pointed to by the end entry so its position is not fixed. Examples of full messages: [ E E E E E E E E . l ] ^ ^ start end <---------------. [ E E . E E E E E E l ] ^ ^ end start Now the end will always point to an unused entry, so TLS 1.3 can always use it.
Showing the changes to include/linux (1 of 4 files). Show all
Unified · Split
| @@ -14,6 +14,7 @@ · 13 unmodified lines | ||
| 14 | 14 | #include <net/strparser.h> |
| 15 | 15 | |
| 16 | 16 | #define MAX_MSG_FRAGS MAX_SKB_FRAGS |
| 17 | +#define NR_MSG_FRAG_IDS (MAX_MSG_FRAGS + 1) | |
| 17 | 18 | |
| 18 | 19 | enum __sk_action { |
| 19 | 20 | __SK_DROP = 0, |
| @@ -29,13 +30,15 @@ struct sk_msg_sg { · 9 unmodified lines | ||
| 29 | 30 | u32 size; |
| 30 | 31 | u32 copybreak; |
| 31 | 32 | unsigned long copy; |
| 32 | − /* The extra element is used for chaining the front and sections when | |
| 33 | − * the list becomes partitioned (e.g. end < start). The crypto APIs | |
| 34 | − * require the chaining. | |
| 33 | + /* The extra two elements: | |
| 34 | + * 1) used for chaining the front and sections when the list becomes | |
| 35 | + * partitioned (e.g. end < start). The crypto APIs require the | |
| 36 | + * chaining; | |
| 37 | + * 2) to chain tailer SG entries after the message. | |
| 35 | 38 | */ |
| 36 | − struct scatterlist data[MAX_MSG_FRAGS + 1]; | |
| 39 | + struct scatterlist data[MAX_MSG_FRAGS + 2]; | |
| 37 | 40 | }; |
| 38 | −static_assert(BITS_PER_LONG >= MAX_MSG_FRAGS); | |
| 41 | +static_assert(BITS_PER_LONG >= NR_MSG_FRAG_IDS); | |
| 39 | 42 | |
| 40 | 43 | /* UAPI in filter.c depends on struct sk_msg_sg being first element. */ |
| 41 | 44 | struct sk_msg { |
| @@ -142,13 +145,13 @@ static inline void sk_msg_apply_bytes(struct sk_psock *psock, u32 bytes) · 100 unmodified lines | ||
| 142 | 145 | |
| 143 | 146 | static inline u32 sk_msg_iter_dist(u32 start, u32 end) |
| 144 | 147 | { |
| 145 | − return end >= start ? end - start : end + (MAX_MSG_FRAGS - start); | |
| 148 | + return end >= start ? end - start : end + (NR_MSG_FRAG_IDS - start); | |
| 146 | 149 | } |
| 147 | 150 | |
| 148 | 151 | #define sk_msg_iter_var_prev(var) \ |
| 149 | 152 | do { \ |
| 150 | 153 | if (var == 0) \ |
| 151 | − var = MAX_MSG_FRAGS - 1; \ | |
| 154 | + var = NR_MSG_FRAG_IDS - 1; \ | |
| 152 | 155 | else \ |
| 153 | 156 | var--; \ |
| 154 | 157 | } while (0) |
| @@ -156,7 +159,7 @@ static inline u32 sk_msg_iter_dist(u32 start, u32 end) · 1 unmodified line | ||
| 156 | 159 | #define sk_msg_iter_var_next(var) \ |
| 157 | 160 | do { \ |
| 158 | 161 | var++; \ |
| 159 | − if (var == MAX_MSG_FRAGS) \ | |
| 162 | + if (var == NR_MSG_FRAG_IDS) \ | |
| 160 | 163 | var = 0; \ |
| 161 | 164 | } while (0) |
| 162 | 165 | |
| @@ -173,9 +176,9 @@ static inline void sk_msg_clear_meta(struct sk_msg *msg) · 10 unmodified lines | ||
| 173 | 176 | |
| 174 | 177 | static inline void sk_msg_init(struct sk_msg *msg) |
| 175 | 178 | { |
| 176 | − BUILD_BUG_ON(ARRAY_SIZE(msg->sg.data) - 1 != MAX_MSG_FRAGS); | |
| 179 | + BUILD_BUG_ON(ARRAY_SIZE(msg->sg.data) - 1 != NR_MSG_FRAG_IDS); | |
| 177 | 180 | memset(msg, 0, sizeof(*msg)); |
| 178 | − sg_init_marker(msg->sg.data, MAX_MSG_FRAGS); | |
| 181 | + sg_init_marker(msg->sg.data, NR_MSG_FRAG_IDS); | |
| 179 | 182 | } |
| 180 | 183 | |
| 181 | 184 | static inline void sk_msg_xfer(struct sk_msg *dst, struct sk_msg *src, |
| @@ -196,14 +199,11 @@ static inline void sk_msg_xfer_full(struct sk_msg *dst, struct sk_msg *src) · 14 unmodified lines | ||
| 196 | 199 | |
| 197 | 200 | static inline bool sk_msg_full(const struct sk_msg *msg) |
| 198 | 201 | { |
| 199 | − return (msg->sg.end == msg->sg.start) && msg->sg.size; | |
| 202 | + return sk_msg_iter_dist(msg->sg.start, msg->sg.end) == MAX_MSG_FRAGS; | |
| 200 | 203 | } |
| 201 | 204 | |
| 202 | 205 | static inline u32 sk_msg_elem_used(const struct sk_msg *msg) |
| 203 | 206 | { |
| 204 | − if (sk_msg_full(msg)) | |
| 205 | − return MAX_MSG_FRAGS; | |
| 206 | − | |
| 207 | 207 | return sk_msg_iter_dist(msg->sg.start, msg->sg.end); |
| 208 | 208 | } |
| 209 | 209 | |