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sys: mitigate possible strncpy string truncation

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gcc 10 with -O2 reports following:

 In function ‘strncpy’,
     inlined from ‘rpc_sys_packagelist’ at /opt/devel/openwrt/c-projects/rpcd/sys.c:244:4:
 /usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ specified bound 128 equals destination size [-Werror=stringop-truncation]
   106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
       |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 In function ‘strncpy’,
     inlined from ‘rpc_sys_packagelist’ at /opt/devel/openwrt/c-projects/rpcd/sys.c:227:4:
 /usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ specified bound 128 equals destination size [-Werror=stringop-truncation]
   106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
       |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Since it is not possible to avoid truncation by strncpy, it is necessary
to make sure the result of strncpy is properly NUL-terminated and the
NUL must be inserted explicitly, after strncpy has returned.

References: #10442
Reported-by: Alexey Smirnov <s.alexey@gmail.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>
This commit is contained in:
Petr Štetiar 2022-08-24 10:05:33 +02:00
parent ae5afea283
commit 82904bd4f9
1 changed files with 3 additions and 3 deletions
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6
sys.c
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@ -172,7 +172,7 @@ rpc_sys_packagelist(struct ubus_context *ctx, struct ubus_object *obj,
struct blob_attr *tb[__RPC_PACKAGELIST_MAX]; struct blob_attr *tb[__RPC_PACKAGELIST_MAX];
int all = false; int all = false;
struct blob_buf buf = { 0 }; struct blob_buf buf = { 0 };
char var[256], pkg[128], ver[128]; char var[256], pkg[128] = { 0 }, ver[128] = { 0 };
char *tmp, *p1, *p2, *p3; char *tmp, *p1, *p2, *p3;
void *tbl; void *tbl;
@ -224,7 +224,7 @@ procstr:
continue; continue;
if (!strcmp(var, "Package:")) { if (!strcmp(var, "Package:")) {
strncpy(pkg, p1, sizeof(pkg)); strncpy(pkg, p1, sizeof(pkg) - 1);
continue; continue;
} }
@ -241,7 +241,7 @@ procstr:
} }
if (!strcmp(var, "Version:")) { if (!strcmp(var, "Version:")) {
strncpy(ver, p1, sizeof(ver)); strncpy(ver, p1, sizeof(ver) - 1);
continue; continue;
} }