Patchwork may go down for maintenance today
Hello, FYI, I'm working on a django and patchwork upgrade on sourceware today so you might see some downtime in the morning and afternoon EDT. Sid
Re: [RFC][PATCH] * bits/confname.h: Define _CS_POSIX_V7_THREADS_CFLAGS, _CS_POSIX_V7_THREADS_LDFLAGS
On 10/27/20 5:03 AM, Érico Nogueira via Libc-alpha wrote: From: Érico Rolim I would like to add these enums in order to conform to the POSIX specification: https://www.man7.org/linux/man-pages/man0/unistd.h.0p.html This change also helps musl-libc, since they want to have these defines with the same values as glibc. I tried to add them for the bits/confname.h and conform/data/unistd.h-data files following the example of the other values, but didn't know how to plug them into the confstr / __sysconf implementations. It's been a while since I touched this code, but IIRC you need to add your new variables to posix/posix-conf-vars.list. That said, could you please let me know if you have a copyright assignment agreement with the FSF? I suppose this change may be OK given that it is under 20 lines but one of the stewards could confirm for sure. Thanks, Siddhesh bits/confname.h| 7 ++- conform/data/unistd.h-data | 2 ++ 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/bits/confname.h b/bits/confname.h index 5dc8215093..fdc5403697 100644 --- a/bits/confname.h +++ b/bits/confname.h @@ -670,6 +670,11 @@ enum _CS_V6_ENV, #define _CS_V6_ENV_CS_V6_ENV -_CS_V7_ENV +_CS_V7_ENV, #define _CS_V7_ENV_CS_V7_ENV + +_CS_POSIX_V7_THREADS_CFLAGS, +#define _CS_POSIX_V7_THREADS_CFLAGS _CS_POSIX_V7_THREADS_CFLAGS +_CS_POSIX_V7_THREADS_LDFLAGS +#define _CS_POSIX_V7_THREADS_LDFLAGS _CS_POSIX_V7_THREADS_LDFLAGS }; diff --git a/conform/data/unistd.h-data b/conform/data/unistd.h-data index aa070528e8..6c4b52a733 100644 --- a/conform/data/unistd.h-data +++ b/conform/data/unistd.h-data @@ -367,6 +367,8 @@ constant _CS_POSIX_V7_LP64_OFF64_LIBS constant _CS_POSIX_V7_LPBIG_OFFBIG_CFLAGS constant _CS_POSIX_V7_LPBIG_OFFBIG_LDFLAGS constant _CS_POSIX_V7_LPBIG_OFFBIG_LIBS +constant _CS_POSIX_V7_THREADS_CFLAGS +constant _CS_POSIX_V7_THREADS_LDFLAGS constant _CS_POSIX_V7_WIDTH_RESTRICTED_ENVS constant _CS_V7_ENV # endif
Re: [PATCH] libdwfl: Rewrite reading of ar_size in elf_begin_rand
On 2022-07-28 09:48, Mark Wielaard wrote:
With GCC 12.1.1, glibc 2.3a, -fsanitize=undefined and
-D_FORTIFY_SOURCE=3 we get the following error message:
In file included from /usr/include/ar.h:22,
from ../libelf/libelfP.h:33,
from core-file.c:31:
In function ‘pread’,
inlined from ‘pread_retry’ at ../lib/system.h:188:21,
inlined from ‘elf_begin_rand’ at core-file.c:86:16,
inlined from ‘core_file_read_eagerly’ at core-file.c:205:15:
/usr/include/bits/unistd.h:74:10: error: ‘__pread_alias’ writing 58 or more
bytes into a region of size 10 overflows the destination
[-Werror=stringop-overflow=]
74 | return __glibc_fortify (pread, __nbytes, sizeof (char),
| ^~~
/usr/include/ar.h: In function ‘core_file_read_eagerly’:
/usr/include/ar.h:41:10: note: destination object ‘ar_size’ of size 10
41 | char ar_size[10]; /* File size, in ASCII decimal. */
| ^~~
/usr/include/bits/unistd.h:50:16: note: in a call to function ‘__pread_alias’
declared with attribute ‘access (write_only, 2, 3)’
50 | extern ssize_t __REDIRECT (__pread_alias,
|^~
cc1: all warnings being treated as errors
The warning disappears when dropping either -fsanitize=undefined
or when using -D_FORTIFY_SOURCE=2. It looks like a false positive.
But I haven't figured out how/why it happens.
Interesting, I'll take a closer look at this from the gcc context. I
obviously don't have any strong opinions about the elfutils patch :)
Thanks,
Sid
The code is a little tricky to proof correct though. The ar_size
field is a not-zero terminated string ASCII decimal, right-paddedr
with spaces. Which is then converted with strtoll. Relying on the
fact that the struct ar_hdr is zero initialized, so there will be
a zero byte after the ar_size field.
Rewrite the code to just use a zero byte terminated char array.
Which is much easier to reason about. As a bonus the error disappears.
Signed-off-by: Mark Wielaard
---
libdwfl/ChangeLog | 5 +
libdwfl/core-file.c | 26 --
2 files changed, 21 insertions(+), 10 deletions(-)
diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index 75c53948..acdaa013 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,8 @@
+2022-07-28 Mark Wielaard
+
+ * core-file.c (elf_begin_rand): Replace struct ar_hdr h with
+ a char ar_size[AR_SIZE_CHARS + 1] array to read size.
+
2022-07-18 Shahab Vahedi
* debuginfod-client.c (dwfl_get_debuginfod_client stub):
diff --git a/libdwfl/core-file.c b/libdwfl/core-file.c
index cefc3db0..4418ef33 100644
--- a/libdwfl/core-file.c
+++ b/libdwfl/core-file.c
@@ -75,26 +75,32 @@ elf_begin_rand (Elf *parent, off_t offset, off_t size,
off_t *next)
from the archive header to override SIZE. */
if (parent->kind == ELF_K_AR)
{
- struct ar_hdr h = { .ar_size = "" };
-
- if (unlikely (parent->maximum_size - offset < sizeof h))
+ /* File size, in ASCII decimal, right-padded with ASCII spaces.
+ Max 10 characters. Not zero terminated. So make this ar_size
+ array one larger and explicitly zero terminate it. As needed
+ for strtoll. */
+ #define AR_SIZE_CHARS 10
+ char ar_size[AR_SIZE_CHARS + 1];
+ ar_size[AR_SIZE_CHARS] = '\0';
+
+ if (unlikely (parent->maximum_size - offset < sizeof (struct ar_hdr)))
return fail (ELF_E_RANGE);
if (parent->map_address != NULL)
- memcpy (h.ar_size, parent->map_address + parent->start_offset + offset,
- sizeof h.ar_size);
+ memcpy (ar_size, parent->map_address + parent->start_offset + offset,
+ AR_SIZE_CHARS);
else if (unlikely (pread_retry (parent->fildes,
- h.ar_size, sizeof (h.ar_size),
+ ar_size, AR_SIZE_CHARS,
parent->start_offset + offset
+ offsetof (struct ar_hdr, ar_size))
-!= sizeof (h.ar_size)))
+!= AR_SIZE_CHARS))
return fail (ELF_E_READ_ERROR);
- offset += sizeof h;
+ offset += sizeof (struct ar_hdr);
char *endp;
- size = strtoll (h.ar_size, &endp, 10);
- if (unlikely (endp == h.ar_size)
+ size = strtoll (ar_size, &endp, 10);
+ if (unlikely (endp == ar_size)
|| unlikely ((off_t) parent->maximum_size - offset < size))
return fail (ELF_E_INVALID_ARCHIVE);
}
Re: [PATCH] libdwfl: Rewrite reading of ar_size in elf_begin_rand
On 2022-07-28 13:27, Siddhesh Poyarekar wrote:
Interesting, I'll take a closer look at this from the gcc context. I
obviously don't have any strong opinions about the elfutils patch :)
I reduced this to the below program and I see it warns with
`-D_FORTIFY_SOURCE=3 -O2 -fsanitize=undefined` as well as
`-D_FORTIFY_SOURCE=2 -O2 -fsanitize=undefined`. This is definitely a
false positive on unreachable code; __pread_alias will never be called
when nbytes is greater than object size.
So I can confirm that this is harmless.
Sid
~~~
typedef long ssize_t;
typedef unsigned long size_t;
typedef long off_t;
struct ar_hdr
{
char ar_mode;
char ar_size[10];
};
extern ssize_t __pread_chk (int fd, void *buf, size_t nbytes, off_t offset,
size_t bufsize)
__attribute__((__access__ (__write_only__, 2, 3)));
extern ssize_t __pread_alias (int fd, void *buf, size_t nbytes, off_t
offset)
__attribute__((__access__ (__write_only__, 2, 3)));
extern ssize_t __pread_chk_warn (int fd, void *buf, size_t nbytes,
off_t offset, size_t bufsize);
extern __inline __attribute__((__always_inline__))
__attribute__((__gnu_inline__)) ssize_t
pread (int fd, void *buf, size_t nbytes, off_t offset)
{
size_t osz = __builtin_dynamic_object_size (buf, 0);
if (__builtin_constant_p (osz) && osz == (size_t) -1)
return __pread_alias (fd, buf, nbytes, offset);
return (((__typeof (nbytes)) 0 < (__typeof (nbytes)) - 1
|| (__builtin_constant_p (nbytes) && (nbytes) > 0))
&& __builtin_constant_p (nbytes <= osz / 1)
&& nbytes <= osz / 1)
? __pread_alias (fd, buf, nbytes, offset)
: __pread_chk (fd, buf, nbytes, offset, osz);
}
ssize_t
pread_retry (int fd, off_t start_offset, off_t offset)
{
ssize_t recvd = 0;
struct ar_hdr h = {.ar_size = {0} };
void *buf = h.ar_size;
size_t len = sizeof (h.ar_size);
off_t off =
start_offset + offset + __builtin_offsetof (struct ar_hdr, ar_size);
do
{
long int res;
do
{
res = pread (fd, ((char *) buf) + recvd, len - recvd, off +
recvd);
}
while (res == -1L);
recvd += res;
}
while ((size_t) recvd < len);
return recvd;
}
