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Subject[PATCH v2 3/3] lib/vsprintf: Hash printed address for netdev bits fallback
The handler for "%pN" falls back to printing the raw pointer value when
using a different format than the (sole supported) special format
"%pNF", potentially leaking sensitive information regarding the kernel
layout in memory.

Avoid this leak by printing the hashed address instead.
Note that there are no in-tree users of the fallback.

Fixes: ad67b74d2469d9b8 ("printk: hash addresses printed with %p")
Signed-off-by: Geert Uytterhoeven <>
Reviewed-by: Petr Mladek <>
- Add Reviewed-by.
lib/vsprintf.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 3ea2119b85ac2e4f..4c75d847c1453ca4 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1510,7 +1510,8 @@ char *restricted_pointer(char *buf, char *end, const void *ptr,

static noinline_for_stack
-char *netdev_bits(char *buf, char *end, const void *addr, const char *fmt)
+char *netdev_bits(char *buf, char *end, const void *addr,
+ struct printf_spec spec, const char *fmt)
unsigned long long num;
int size;
@@ -1521,9 +1522,7 @@ char *netdev_bits(char *buf, char *end, const void *addr, const char *fmt)
size = sizeof(netdev_features_t);
- num = (unsigned long)addr;
- size = sizeof(unsigned long);
- break;
+ return ptr_to_id(buf, end, addr, spec);

return special_hex_number(buf, end, num, size);
@@ -1949,7 +1948,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
return restricted_pointer(buf, end, ptr, spec);
case 'N':
- return netdev_bits(buf, end, ptr, fmt);
+ return netdev_bits(buf, end, ptr, spec, fmt);
case 'a':
return address_val(buf, end, ptr, fmt);
case 'd':
 \ /
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