* [PATCH] mips: dl-machine-reject-phdr: Get rid of alloca.
@ 2023-06-22 16:06 Joe Simmons-Talbott
2023-06-23 13:26 ` Joe Simmons-Talbott
0 siblings, 1 reply; 2+ messages in thread
From: Joe Simmons-Talbott @ 2023-06-22 16:06 UTC (permalink / raw)
To: libc-alpha; +Cc: Joe Simmons-Talbott
Use a scratch_buffer rather than alloca to avoid potential stack overflow.
Checked with build-many-glibcs.py on mips-linux-gnu
---
sysdeps/mips/dl-machine-reject-phdr.h | 80 +++++++++++++++++++++------
1 file changed, 62 insertions(+), 18 deletions(-)
diff --git a/sysdeps/mips/dl-machine-reject-phdr.h b/sysdeps/mips/dl-machine-reject-phdr.h
index 104b590661..7217d2d439 100644
--- a/sysdeps/mips/dl-machine-reject-phdr.h
+++ b/sysdeps/mips/dl-machine-reject-phdr.h
@@ -20,6 +20,7 @@
#define _DL_MACHINE_REJECT_PHDR_H 1
#include <unistd.h>
+#include <scratch_buffer.h>
#include <sys/prctl.h>
#if defined PR_GET_FP_MODE && defined PR_SET_FP_MODE
@@ -167,6 +168,8 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
unsigned int cur_mode = -1;
# if HAVE_PRCTL_FP_MODE
bool cannot_mode_switch = false;
+ struct scratch_buffer sbuf;
+ scratch_buffer_init (&sbuf);
/* Get the current hardware mode. */
cur_mode = __prctl (PR_GET_FP_MODE);
@@ -182,17 +185,29 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
mips_abiflags = (Elf_MIPS_ABIFlags_v0 *) (buf + ph->p_offset);
else
{
- mips_abiflags = alloca (size);
+ if (!scratch_buffer_set_array_size (&buf, 1, size))
+ REJECT (" unable to allocate memory\n");
+ mips_abiflags = buf.data;
+
__lseek (fd, ph->p_offset, SEEK_SET);
if (__libc_read (fd, (void *) mips_abiflags, size) != size)
- REJECT (" unable to read PT_MIPS_ABIFLAGS\n");
+ {
+ scratch_buffer_free (&sbuf);
+ REJECT (" unable to read PT_MIPS_ABIFLAGS\n");
+ }
}
if (size < sizeof (Elf_MIPS_ABIFlags_v0))
- REJECT (" contains malformed PT_MIPS_ABIFLAGS\n");
+ {
+ scratch_buffer_free (&sbuf);
+ REJECT (" contains malformed PT_MIPS_ABIFLAGS\n");
+ }
if (__glibc_unlikely (mips_abiflags->flags2 != 0))
- REJECT (" unknown MIPS.abiflags flags2: %u\n", mips_abiflags->flags2);
+ {
+ scratch_buffer_free (&sbuf);
+ REJECT (" unknown MIPS.abiflags flags2: %u\n", mips_abiflags->flags2);
+ }
in_abi = mips_abiflags->fp_abi;
}
@@ -202,7 +217,10 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
/* Unknown ABIs are rejected. */
if (in_abi != -1 && in_abi > Val_GNU_MIPS_ABI_FP_MAX)
- REJECT (" uses unknown FP ABI: %u\n", in_abi);
+ {
+ scratch_buffer_free (&sbuf);
+ REJECT (" uses unknown FP ABI: %u\n", in_abi);
+ }
/* Obtain the initial requirements. */
in_req = (in_abi == -1) ? none_req : reqs[in_abi];
@@ -215,7 +233,10 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
struct abi_req existing_req;
if (cached_fpabi_reject_phdr_p (l))
- return true;
+ {
+ scratch_buffer_free (&sbuf);
+ return true;
+ }
#if _MIPS_SIM == _ABIO32
/* A special case arises for O32 FP64 and FP64A where the kernel
@@ -229,8 +250,11 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
if ((l->l_mach.fpabi == Val_GNU_MIPS_ABI_FP_64A
|| l->l_mach.fpabi == Val_GNU_MIPS_ABI_FP_64)
&& cur_mode == -1)
- REJECT (" found %s running in the wrong mode\n",
- fpabi_string (l->l_mach.fpabi));
+ {
+ scratch_buffer_free (&sbuf);
+ REJECT (" found %s running in the wrong mode\n",
+ fpabi_string (l->l_mach.fpabi));
+ }
#endif
/* Found a perfect match, success. */
@@ -238,7 +262,10 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
/* Unknown ABIs are rejected. */
if (l->l_mach.fpabi != -1 && l->l_mach.fpabi > Val_GNU_MIPS_ABI_FP_MAX)
- REJECT (" found unknown FP ABI: %u\n", l->l_mach.fpabi);
+ {
+ scratch_buffer_free (&sbuf);
+ REJECT (" found unknown FP ABI: %u\n", l->l_mach.fpabi);
+ }
existing_req = (l->l_mach.fpabi == -1 ? none_req
: reqs[l->l_mach.fpabi]);
@@ -262,9 +289,12 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
#endif
}
else
- REJECT (" uses %s, already loaded %s\n",
- fpabi_string (in_abi),
- fpabi_string (l->l_mach.fpabi));
+ {
+ scratch_buffer_free (&sbuf);
+ REJECT (" uses %s, already loaded %s\n",
+ fpabi_string (in_abi),
+ fpabi_string (l->l_mach.fpabi));
+ }
}
#if _MIPS_SIM == _ABIO32
@@ -281,7 +311,10 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
If the overall requirements cannot be met by FR0 then reject the
object. */
if (cur_mode == -1)
- return !in_req.fr0;
+ {
+ scratch_buffer_free (&sbuf);
+ return !in_req.fr0;
+ }
# if HAVE_PRCTL_FP_MODE
{
@@ -293,9 +326,12 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
can be either the FR1 mode or FR0 if the requirements are met by
FR0. */
if (cannot_mode_switch)
- return (!(in_req.fre && cur_mode == (PR_FP_MODE_FR | PR_FP_MODE_FRE))
- && !(in_req.fr1 && cur_mode == PR_FP_MODE_FR)
- && !(in_req.fr0 && cur_mode == 0));
+ {
+ scratch_buffer_free (&sbuf);
+ return (!(in_req.fre && cur_mode == (PR_FP_MODE_FR | PR_FP_MODE_FRE))
+ && !(in_req.fr1 && cur_mode == PR_FP_MODE_FR)
+ && !(in_req.fr0 && cur_mode == 0));
+ }
/* If the overall requirements can be satisfied by FRE but not FR1 then
fr1_mode must become FRE. */
@@ -305,14 +341,21 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
/* Set the new mode. Use fr1_mode if the requirements cannot be met by
FR0. */
if (!in_req.fr0)
- return __prctl (PR_SET_FP_MODE, fr1_mode) != 0;
+ {
+ scratch_buffer_free (&sbuf);
+ return __prctl (PR_SET_FP_MODE, fr1_mode) != 0;
+ }
else if (__prctl (PR_SET_FP_MODE, /* fr0_mode */ 0) != 0)
{
/* Setting FR0 can validly fail on an R6 core so retry with the FR1
mode as a fall back. */
if (errno != ENOTSUP)
- return true;
+ {
+ scratch_buffer_free (&sbuf);
+ return true;
+ }
+ scratch_buffer_free (&sbuf);
return __prctl (PR_SET_FP_MODE, fr1_mode) != 0;
}
}
@@ -320,6 +363,7 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
}
#endif /* _MIPS_SIM == _ABIO32 */
+ scratch_buffer_free (&sbuf);
return false;
}
--
2.39.2
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] mips: dl-machine-reject-phdr: Get rid of alloca.
2023-06-22 16:06 [PATCH] mips: dl-machine-reject-phdr: Get rid of alloca Joe Simmons-Talbott
@ 2023-06-23 13:26 ` Joe Simmons-Talbott
0 siblings, 0 replies; 2+ messages in thread
From: Joe Simmons-Talbott @ 2023-06-23 13:26 UTC (permalink / raw)
To: libc-alpha
On Thu, Jun 22, 2023 at 12:06:25PM -0400, Joe Simmons-Talbott wrote:
> Use a scratch_buffer rather than alloca to avoid potential stack overflow.
>
> Checked with build-many-glibcs.py on mips-linux-gnu
> ---
> sysdeps/mips/dl-machine-reject-phdr.h | 80 +++++++++++++++++++++------
> 1 file changed, 62 insertions(+), 18 deletions(-)
>
> diff --git a/sysdeps/mips/dl-machine-reject-phdr.h b/sysdeps/mips/dl-machine-reject-phdr.h
> index 104b590661..7217d2d439 100644
> --- a/sysdeps/mips/dl-machine-reject-phdr.h
> +++ b/sysdeps/mips/dl-machine-reject-phdr.h
> @@ -20,6 +20,7 @@
> #define _DL_MACHINE_REJECT_PHDR_H 1
>
> #include <unistd.h>
> +#include <scratch_buffer.h>
> #include <sys/prctl.h>
>
> #if defined PR_GET_FP_MODE && defined PR_SET_FP_MODE
> @@ -167,6 +168,8 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
> unsigned int cur_mode = -1;
> # if HAVE_PRCTL_FP_MODE
> bool cannot_mode_switch = false;
> + struct scratch_buffer sbuf;
> + scratch_buffer_init (&sbuf);
>
> /* Get the current hardware mode. */
> cur_mode = __prctl (PR_GET_FP_MODE);
> @@ -182,17 +185,29 @@ elf_machine_reject_phdr_p (const ElfW(Phdr) *phdr, unsigned int phnum,
> mips_abiflags = (Elf_MIPS_ABIFlags_v0 *) (buf + ph->p_offset);
> else
> {
> - mips_abiflags = alloca (size);
> + if (!scratch_buffer_set_array_size (&buf, 1, size))
&sbuf
> + REJECT (" unable to allocate memory\n");
> + mips_abiflags = buf.data;
sbuf.data
v2 will be posted soon.
Thanks,
Joe
^ permalink raw reply [flat|nested] 2+ messages in thread
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